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With the increasing popularity of green fuel and the rapid growth of the marine economy, the maintenance of ship main engines, especially cylinder liners, has become a crucial issue. In this paper, we introduce a novel continuous spiral line laser scanning infrared non-destructive testing (Cslls Ir NDT) method and device for detecting scratch defects on the working surface of ship engine cylinder liners, aiming to achieve efficient and automated detection without disassembling the engine. Through numerical simulations of line laser scanning infrared NDT, we have effectively detected scratches with widths ranging from 0.05 to 1 mm and depths from 0.1 to 1.5 mm. The scanning path of the Cslls IR NDT was analysed, and the scanning images were simulated. Subsequently, the spatial reconstruction and optimisation of the scanning images were completed using pseudo-static matrix reconstruction (PSMR) and Fourier series fitting, and feature image extraction algorithms were applied to extract the feature image. Ultimately, the 3D infrared thermography visualisation of the cylinder liner was achieved through cylindrical surface mapping. The automatic detection method and device proposed in this paper provide valuable theoretical support and reference for the subsequent maintenance and repair of cylinder liners and other key tubular components. [ABSTRACT FROM AUTHOR]

As virtual reality (VR) technology advances, the use of VR scenarios and applications is becoming increasingly prevalent, and the fatigue issues associated with existing mid-air hand interactions are becoming more pronounced. To alleviate fatigue in VR interactions, we developed a desktop interaction system, BeyondDeskVR. Designed for seamless integration with mid-air hand interaction in seated VR work environments, the system enables portable interaction input and mode switching. By extending virtual hand interactions to the desktop space, the system could be used on any desktop. We utilised infrared laser projection for desktop gesture recognition and achieved seamless transitions between desktop gesture interactions and mid-air hand interactions in typical three-dimensional scenarios, including pointing and selection, user interface interaction, and object manipulation. We conducted a comprehensive evaluation of the BeyondDeskVR gesture interaction system and mid-air hand interaction using a pointing selection task, assessing their performance in terms of subjectivity, performance, and fatigue. The results indicate that the BeyondDeskVR system has high user acceptance, significantly lower fatigue than does mid-air hand interaction, and comparable interaction efficiency and accuracy. Integrating this system with mid-air hand interaction can effectively reduce fatigue in VR interactions and enhance the overall VR experience. [ABSTRACT FROM AUTHOR]

To achieve non-destructive detection of crack depth in the process of notching and cracking of metal bars in low-stress cropping, a quantitative detection method for crack depth of notched bars based on infrared thermography technology under laser excitation is proposed in this paper. Combined with physical experiments, a simulation model of the temperature distribution of the laser-excited bar is established for efficient data acquisition, and the temperature curves of the bar surface under laser excitation are analysed from the perspective of space and time. On this basis, the study selects the feature parameters of the three types of defects on the surface of the metal bar, namely notch, surface crack and crack of notch bottom. A backpropagation (BP) neural network model is established for crack depth by dividing the crack into two types of a notch with crack and unnotched crack, and compared with other common prediction models. The results show that the selected features can accurately characterise the cracks in this BP neural network model, and the detected error in crack depth assessment is less than 3%. Performance metrics are established to evaluate the model, which has good reliability under different noises. [ABSTRACT FROM AUTHOR]

A nanocomposite (NC) of polyaniline (Pani), polyvinyl pyrrolidone (PVP) and zinc sulfide (ZnS) nanoparticles (NP) was prepared using chemical coprecipitation and ex-situ casting procedures. ZnS NP were synthesized using the chemical coprecipitation technique in atmospheric air. The x-ray diffraction (XRD) scans indicated that the synthesized ZnS had a nanonature and fit the cubic zinc blended structure. We used an infrared pulsed laser to irradiate the Pani/PVP/ZnS NC samples with fluences ranging from 3 to18 J/cm2. The induced changes in the NC were investigated using the UV spectroscopy and International Commission on Illumination (CIE) color difference methodology. When the laser fluence increased up to 18 J/cm2 both the direct and indirect optical bandgaps (Eg) decreased. Additionally, we used the optical dielectric loss (ε") to detect the type of microelectronic transition for the NC samples. The Eg of the exposed NC samples and the pristine samples exhibited indirect allowed transitions. The laser effects on the absorbance, extinction coefficient, transmission, refractive index, dielectric parameters and optical conductivity of the NC were studied. Lastly, the color differences between the pristine and exposed samples were determined. The pristine Pani/PVP/ZnS showed a significant color difference with the laser irradiated samples. The changes of the studied optical parameters with the laser fluence indicated that the laser radiation represents a convenient tool that would allow the application of Pani/PVP/ZnS NC in optoelectronic devices. [ABSTRACT FROM AUTHOR]

AbstractNanocomposite films (NC) of amorphous polycarbonate (PC), semicrystalline polyethylene oxide (PEO), and chromium oxide (Cr2O3) nanoparticles (NP) were synthesized. We believe that this study is novel in the area of the effect of laser radiation on such NC. The synthesized Cr2O3 had a nanonature of average particle size 29 nm, as indicated from the Rietveld refinement of the XRD scans. Samples of the PC-PEO/Cr2O3 NC films were irradiated with infrared energy fluences ranging from 5 to 95 Joule/cm2 (J/cm2) using an infrared pulsed laser. We used UV-vis spectroscopy and the International Commission on Illumination (CIE) color changes technique to investigate the resulting effects of the laser irradiation on the optical bandgap energy and color properties of the prepared films. As the laser fluence increased up to 95 J/cm2, the maximum fluence used, both the direct and indirect bandgaps decreased. The Urbach energy showed an opposite tendency; it increased from 0.32 to 0.56 eV. This can be attributed to the dominance of chain crosslinks that destroyed the ordered structure and thus increased the amorphous regions. Also, the optical dielectric loss (ε″) aided in detecting the nature of the microelectronic transitions. It was found that the PC/PEO/Cr2O3 NC films had direct allowed transitions. Additionally, the effect of laser irradiation on the absorbance, refractive index, real and imaginary dielectric parameters, and optical conductivity of the blend composite samples were studied. Moreover, the optical color changes between the pristine and the irradiated films were evaluated. The pristine blend film was uncolored. It showed significant color changes when irradiated with the laser at increasing fluences up to 95 J/cm2. The change in the optical properties of PC/PEO/Cr2O3 NC film suggested its usage as a promising candidate for future optoelectronics manufacturing. [ABSTRACT FROM AUTHOR]

To elucidate whether it is feasible to use porcine eyes from scalded, abattoir-acquired animals for refractive femtosecond laser research. An infrared laser (FS 200) and an ultraviolet laser (prototype version) were tested for their applicability on scalded pig eyes. Fifty porcine eyes were divided into two equally-sized groups and assigned to either the infrared or the ultraviolet laser. Both laser groups were comprised of five subgroups of n = 5 eyes each. Group A: non-scalded eyes (negative control); group B: eyes taken from tunnel-scalded animals; group C1: eyes taken from tank-scalded animals without opaque corneal lesion; group C2: eyes taken from animals with opaque corneal lesion; group D: eyes scalded in toto in the laboratory (positive control). In each group the lasers were employed to create a stromal flap. The quality of the laser cuts and the resulting flap beds, as well as of the porcine corneas themselves, was examined by anterior segment optical coherence tomography and scanning electron microscopy. All scalded specimens exhibited substantial corneal swelling, most pronounced in group C2. After ultraviolet laser application, the tank- and tunnel-scalded samples displayed marked irregularities and an increased degree of surface roughness in the flap beds. After infrared laser application, this was only the case in the tank-scalded specimens. It is not recommended to use eyes taken from scalded pigs for ultraviolet femtosecond laser experiments. For infrared femtosecond lasers, eyes taken from tunnel-scalded animals may represent an acceptable alternative, if non-scalded eyes are not available. [ABSTRACT FROM AUTHOR]

Amused with the blissful benefits of micro-textures, researchers consider it a promising option for improving cutting tool performance, especially during machining superalloys. Through this study, the machining performance of two homothetic and six hybrid micro-textured tungsten carbide inserts have been comparatively assessed while dry turning Inconel-718. Dimple and channel micro-textures were the two independent homothetic textures. Dimple and channel micro-textures with 0°, 45°, and 90° orientation angles and a combination of triangle, square, and dimples constituted six different hybrid micro-textures. Micro-textures were fabricated on the rake face of inserts using a Ti-sapphire fired, nanosecond pulsed, infrared fiber laser. Dimple and channel micro-textured tools at 90° texture angle on rake face performed exceptionally well. Improvements in average tool life, cutting forces, and surface finish have been reported. Adhesion and attrition were the predominant forms of tool wear. Chip morphology study revealed long helical and continuous but segmented chips. [ABSTRACT FROM AUTHOR]

Methanol is one of the most abundant interstellar Complex Organic Molecules (iCOMs) and represents a major building block for the synthesis of increasingly complex oxygen-containing molecules. The reaction between protonated methanol and its neutral counterpart, giving protonated dimethyl ether, $ \require{mhchem} \ce{(CH3)2OH+} $ (CH 3 ) 2 OH + , along with the ejection of a water molecule, has been proposed as a key reaction in the synthesis of dimethyl ether in space. Here, gas phase vibrational spectra of the $ \ce{(CH3)2OH+} $ (CH 3 ) 2 OH + reaction product and the $ \ce{[C2H9O2]+} $ [ C 2 H 9 O 2 ] + intermediate complex(es), formed under different pressure and temperature conditions, are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to record these vibrational fingerprint spectra using different types of infrared action spectroscopy in the 600-1700 cm $ ^{-1} $ − 1 frequency range, complemented with measurements using an OPO/OPA system to cover the $ \ce{O-H} $ O − H stretching region $ 3400-3700\,{\rm cm}^{-1} $ 3400 − 3700 c m − 1 . The formation of protonated dimethyl ether as a product of the reaction is spectroscopically confirmed, providing the first gas-phase vibrational spectrum of this potentially relevant astrochemical ion. [ABSTRACT FROM AUTHOR]

High-resolution Fourier transform spectroscopy and Laser-induced fluorescence have been performed on LiCa in the infrared spectral range. We analyse rovibrational transitions of the (2) 2 Σ + – X (1) 2 Σ + system of LiCa and find the (2) 2 Σ + state to be perturbed by spin–orbit coupling to the (1) 2 Π state. We study the coupled system obtaining molecular parameters for the (2) 2 Σ + and the (1) 2 Π state together with effective spin–orbit and spin–rotation coupling constants. The coupled system has also been evaluated by applying a potential function instead of rovibrational molecular parameters for the state (2) 2 Σ + . An improved analytic potential function of the X (1) 2 Σ + state is derived, due to the extension of the observed rotational ladder. [ABSTRACT FROM AUTHOR]

Aluminium alloys are difficult to be manufactured by directed energy deposition (DED) with the widely used infrared laser because of the low absorptivity. A blue laser with a 450 nm wavelength has a significantly higher laser absorptivity in processing aluminium. Here, we developed a 2000 W blue laser directed energy deposition (BL-DED) system for additive manufacturing. In this system, a coaxial camera, a paraxial high-speed camera, and a paraxial infrared camera were simultaneously adopted to analyze the formation and evolution of molten pool characteristics. The relationships among the molten pool characteristics, depositing states, and appearance defects were built. We successfully printed the curved thin wall with good appearance quality by the manual in-situ control of appearance defects. This work demonstrated the advantages of the blue laser in DED of aluminium alloy, which could melt the powders under lower energy input conditions and result in a more stable deposition process. [ABSTRACT FROM AUTHOR]

Laser surface pretreatment is an effective approach for improving the mechanical properties of adhesive joints. In the case of laser surface treatment of carbon fibre reinforced polymer (CFRP), ultraviolet (UV) lasers and lower pulse fluence infrared (IR) lasers are usually used to ensure the surface pretreatment quality. With respect to improving the surface treatment efficiency as much as possible, the influence of higher pulse fluence (12.7 J/cm2) IR laser pretreatment parameters on the mechanical properties of CFRP/aluminium alloy hybrid joints were investigated in this study. Scanning electron microscopy (SEM), contact angle measurements, confocal laser scanning microscope (CLSM), and X-ray photoelectron spectroscopy (XPS) were used to analyse the surface modification and failure modes of the adhesive surface. Additionally, the influence of the IR laser pretreatment parameters on the failure mode of CFRP/aluminium alloy adhesive joints under tension loading was discussed. The results showed that in addition to surface free energy, subsurface damage and mechanical interlocking were important factors affecting the shear strength of CFRP/aluminium alloy adhesive joints when a higher pulse fluence IR laser was applied for surface pretreatment. Finally, the optimized laser surface pretreatment parameters considering both the treatment efficiency and quality were obtained for the CFRP/aluminium alloy adhesive joint. [ABSTRACT FROM AUTHOR]

The results of the study of high conducting areas at the interface between ferroelectric and insulating oxides Ba0.8Sr0.2TiO3/LaMnO3 are presented. It is shown that the electrical resistance of the heterostructure decreases significantly with cooling and exhibits metallic behavior at low temperatures, and its properties depend on magnetic field application. The effect of green (514 nm) and infrared (1028 nm) pulsed laser light on Ba0.8Sr0.2TiO3/LaMnO3 heterostructure electrical resistance leads to a decrease in the electrical resistance. It is assumed that the effect is related to polarization screening in the ferroelectric film, and atomic force microscopy studies confirm this hypothesis. [ABSTRACT FROM AUTHOR]

After being launched into orbit, the geometric calibration of a satellite laser altimeter will reduce errors in laser pointing and ranging caused by satellite vibrations during launch, environmental changes, and thermal effects during long-term operation, which guarantees the accuracy of measurement data. In this study, a satellite laser geometric calibration method combining infrared detectors and corner-cube retroreflectors (CCRs) is proposed. First, a CCR-based laser ranging error calibration method was established, and then a laser pointing error calibration model was derived based on a single infrared detector array. Taking GaoFen-7 (GF-7) satellite laser beam 2 as the experimental object, laser geometric calibration was realized using an infrared detector and CCR-measured data. Then, the accuracy of the proposed method was compared with that of other calibration methods, the CMLID and the CMSPR. The results show that the accuracy of the proposed calibration method is equivalent to that of the CMLID and higher than that of the CMSPR. Among them, the accuracy of the laser pointing after calibration using the proposed method is better than 0.8 arcsec, and the elevation accuracy of the laser on flat, sloping, and mountainous terrains is better than 0.11 m, 0.30 m, and 1.80 m, respectively. [ABSTRACT FROM AUTHOR]

In the present work, we used the ex situ casting technique to synthesize a nanocomposite (NC) of polyvinyl alcohol (PVA) and nanosize palladium (Pd). The Pd has a particle size in the range from 2 to 22 nm with 10 nm on average. Samples from the synthesized NC have been irradiated with different fluences ranging from 2 to 20 J/cm2 from GaAs infrared pulsed laser (5-watt power, 904 nm wavelength, 200 ns pulse duration, 1200 Hz frequency and 0.28 cm2 spot area). Nonisothermal crystallization kinetics of the synthesized NC was investigated using differential scanning calorimetry (DSC) with different cooling rates. The Jeziorny and Mo approaches were applied to describe the nonisothermal analysis. Several nonisothermal kinetic parameters, such as the crystallization peak temperature (Tc), the enthalpy of crystallization (ΔHc), the degree of crystallinity (Xc), the crystallization halftime (t1/2), the Avrami exponent (n) and the activation of crystallization (Ea) were evaluated and interpreted as a function of laser fluences. The results indicated that the incorporation Pd nanoparticles into the PVA matrix accelerate the crystallization process, while the laser radiation causes chain crosslinking that reduces the crystallinity. [ABSTRACT FROM AUTHOR]

Non-ablative fractional laser (NAFL) and radiofrequency (RF) are popular for treating periorbital wrinkles owing to short downtime and low risk of side effects. To compare the effectiveness and safety of infrared bipolar radiofrequency (IR-RF) and NAFL, including 1540 nm Er: glass and 1927 nm thulium-doped laser, to determine the better option for clinical treatment of periorbital wrinkles. Twenty-seven patients assigned to 3 groups underwent split-face treatment. Two of the three treatments were randomly selected for patients in each group: IR-RF, 1540 nm Er: glass NAFL, and 1927 nm thulium-doped NAFL. Therapeutic outcomes were subjectively and objectively evaluated six months after the last treatment. Side effects and pain evaluations were conducted. Fitzpatrick wrinkle scores revealed no statistical difference for IR-RF, whereas the NAFL-treated sides exhibited significant improvements (p <.05). VISIA analysis of skin texture showed similar results. In IR-RF-treated sides, patients over 50 years old exhibited significant improvements compared with those below 50 (p <.05). The sample size was small. More objective evaluations like photometer measurements are required. NAFL is effective and safe for improving periorbital wrinkles, but IR-RF might be more suitable for elderly patients, particularly those with low pain tolerance. [ABSTRACT FROM AUTHOR]

Laser measurements of the intensity of (201) 3 22 − (000) 2 21 near-infrared water absorption line at 10,670.1 cm − 1 are made using three different Herriott cells. These measurements determine the line intensity with an standard deviation below of 0.3% by consideration of the new geometrically derived formula for the optical path length without approximations. This determination together with the current accepted value lead to an overall uncertainty of 0.7% of the experimentally assessed line intensity which is compared with previous ab initio predictions. It is found that steady improvements in both the dipole moment surface (DMS) and the potential energy surface (PES) used in the theoretical studies lead to a systematically better agreement with the observation, with the most recent prediction agreeing closely with the experiment. [ABSTRACT FROM AUTHOR]

We report the absolute frequency of the v ′ = 1 , N ′ = 2 ← v ″ = 0 , N ″ = 0 vibrational transition in the X 1 Σ + electronic ground state of D 2 . Deuterium molecules in the v ″ = 0 , N ″ = 0 state in a molecular beam are excited to v ′ = 1 , N ′ = 2 using a narrow-linewidth continuous-wave laser stabilised to an optical frequency comb; a strong static electric field in the excitation region induces a transition dipole moment, greatly enhancing the transition strength. Molecules excited to v ′ = 1 , N ′ = 2 are state-selectively ionised using a pulsed ultraviolet laser and mass-selectively detected. Spectra recorded by scanning the infrared laser frequency are fit with a multi-Gaussian model that accounts for the intensities and relative frequencies of all hyperfine components at the static electric field strength used in the measurement. Zero-field absolute transition frequencies were determined from fits of 28 spectra recorded at nine different field strengths. Statistical uncertainty and systematic uncertainties due to the field plate spacing and relative intensities of the hyperfine components comprise the bulk of the overall uncertainty. We determine an absolute S 1 (0) transition frequency of 94,925,100,487(17) kHz after correcting for the photon recoil and second-order Doppler shifts. This value agrees with other recent experimental measurements and a theoretical prediction, but with a lower fractional uncertainty of only 0.2 ppb. [ABSTRACT FROM AUTHOR]

The vibrational predissociation spectra of the CN–H2 and CN–D2 complexes are measured in regions between 450 and 3100 cm − 1 in an ion trap at different temperatures at the free electron lasers for infrared experiments (FELIX) Laboratory. Strong differences between the vibrational spectra of the two para and ortho nuclear spin isomers (CN–(p-H2) or CN–(o-H2) and CN–(p-D2) or CN–(o-D2)) are detected. In the case of CN–H2 we could assign the observed bands with the help of an accurate quantum calculation. The spectrum is dominated by the first overtone of the hindered H2 rotation in combination with the hindered CN rotation of the CN–(o-H2) nuclear spin isomer. The energetically higher-lying CN–(p-H2) isomer was not observed due to efficient ortho-para ligand exchange. The C–N stretching mode was recorded at 2040(1) cm − 1 . For the CN–D2 system several vibrational modes of both spin isomers overlap in their low-lying intermonomer streching and bending region, but the main observed bands are attributed to the more stable CN–(p-D2) spin isomer. The D–D stretching vibration was found to be at 2898(1) cm − 1 . [ABSTRACT FROM AUTHOR]

The vibrational predissociation spectra of the CN–H2 and CN–D2 complexes are measured in regions between 450 and 3100 cm − 1 in an ion trap at different temperatures at the free electron lasers for infrared experiments (FELIX) Laboratory. Strong differences between the vibrational spectra of the two para and ortho nuclear spin isomers (CN–(p-H2) or CN–(o-H2) and CN–(p-D2) or CN–(o-D2)) are detected. In the case of CN–H2 we could assign the observed bands with the help of an accurate quantum calculation. The spectrum is dominated by the first overtone of the hindered H2 rotation in combination with the hindered CN rotation of the CN–(o-H2) nuclear spin isomer. The energetically higher-lying CN–(p-H2) isomer was not observed due to efficient ortho-para ligand exchange. The C–N stretching mode was recorded at 2040(1) cm − 1 . For the CN–D2 system several vibrational modes of both spin isomers overlap in their low-lying intermonomer streching and bending region, but the main observed bands are attributed to the more stable CN–(p-D2) spin isomer. The D–D stretching vibration was found to be at 2898(1) cm − 1 . [ABSTRACT FROM AUTHOR]

The lithium bismuth aluminum borate glasses doped with Er3+ ion (LiBiAlB:Er) were investigated for laser and optical amplifier applications by the Judd–Ofelt and MacCumber theory. The LiBiAlB:Er glass with optimum Er2O3 concentration, 1.0 mol%, then was selected to enhance the luminescence properties by co-doping with the Yb3+ ion. The Er3+/Yb3+ co-doped glasses (LiBiAlB:ErYb) were prepared and studied in the physical, optical, glass network, absorption, and luminescence properties. The glass density tends to increase with addition of Yb2O3 concentration. The FTIR spectra perform the main glass structure which composes of the trigonal BO3 and tetrahedral BO4 borate groups mixing with AlO6 complex. The improvement of absorption coefficient around 977 nm by doping with Yb3+ results in the enhancement of Er3+ emission intensity at 1536 nm wavelength (4I13/2 → 4I15/2). The Yb3+→ Er3+ energy transfer is a significant factor of luminescence development in LiBiAlB:ErYb glass. The MacCumber analysis confirms the high potential for using LiBiAlB:ErYb glass, with Er2O3 1.0 mol% and Yb2O3 2.0 mol%, as an infrared laser medium and a fiber optics amplifier. [ABSTRACT FROM AUTHOR]

Laser absorption spectroscopy combined with spectral analysis has been extensively investigated in detection and measurements of gas samples because of their broad applicability for measuring more than one hundred species, such as O2, CO2, H2O, HCl, NH3, NOx, and hydrocarbons. Recently, real-time detection and measurements of gas samples based on laser absorption spectroscopy have attracted considerable interest from various fields owing to their performance of robustness, fast response speed, high sensitivity, and good precision. Here, we review the commonly used infrared laser absorption spectroscopy techniques for real-time measurements and the significant optical equipment utilized in measuring systems. Then, we discuss practical applications based on infrared laser absorption spectroscopy which require real-time determination of gas component concentrations, including atmospheric environment monitoring, breath analysis, combustion diagnostics, and industrial applications. Finally, perspectives of real-time determination of gas component concentrations based on infrared laser absorption spectroscopy are presented. [ABSTRACT FROM AUTHOR]

The Bayfol UV1 7-2 is a set of polymeric solid-state nuclear track detectors with several applications in radiation detection fields. Samples from Bayfol film have been exposed to infrared pulsated laser with different fluences (10–115 J/cm2). The outcome of laser irradiation on the structural and optical properties of the Bayfol samples has been studied using X-ray diffraction and UV spectroscopy. Various optical parameters, such as the optical energy gap, Urbach energy, refractive index, optical dielectric constant, tristimulus values, chromaticity coordinates, color intercepts and color intensity, have been calculated and discussed as a function of laser fluences. The optical energy gap decreased by increasing the laser fluence up to 115 J/cm2 and an increase in the Urbach energy. This could be due to the domination of crosslinking that destroys the ordered structure. Furthermore, the non-irradiated Bayfol is nearly colorless. It displays a significant color difference by laser irradiation. [ABSTRACT FROM AUTHOR]

Extensive infrared spectra of the weakly-bound CO2-CO dimer are observed in the carbon dioxide ν3 asymmetric stretch region (≈2350 cm−1) using a tunable infrared OPO laser source to probe a pulsed slit jet supersonic expansion. Both C-bonded and O-bonded isomers are analysed for the normal isotopologue as well as for 13CO2-CO and 16O13C18O-CO, the latter being the first observation of an asymmetrically substituted form for which all values of Ka are allowed. Combination bands involving the lowest in-plane intermolecular bending modes are also studied for both isomers. Weak bands near 2337 cm−1 are assigned to CO2 hot band transitions (v1, v 2 l 2 , v3) = (0111) ← (0110), yielding the splitting of the degenerate CO2 ν2 bend into in-plane and out-of-plane components due to the presence of the CO. This splitting has rather different values for the C- and O- bonded isomers, 4.57 and 1.59 cm−1, respectively, with the out-of-plane mode higher in energy than the in-plane for both cases. [ABSTRACT FROM AUTHOR]

Photoelectron images have been measured following the ionisation of aligned distributions of gas phase naphthalene and aniline molecules. Alignment in the adiabatic regime was achieved by interaction with a 100 ps infrared laser pulse, with ionisation achieved in a two-photon resonant scheme using a low intensity UV pulse of ∼6 ps duration. The resulting images are found to exhibit anisotropy that increases when the alignment pulse is present, with the aniline PADs peaking along the polarisation vector of the ionising light and the naphthalene PADs developing a characteristic four-lobed structure. Photoelectron angular distributions (PADs) that result from the ionisation of unaligned and fully aligned distributions of molecules are calculated using the ePolyScat ab initio suite and converted into two-dimensional photoelectron images. In the case of naphthalene excellent agreement is observed between experiment and the simulation for the fully aligned distribution, showing that the alignment step allows us to probe the molecular frame, but in the case of aniline it is clear that additional processes occur following the one-photon resonant step. [ABSTRACT FROM AUTHOR]

The carbon chain ions HC 3 O + and HC 3 S + – longer variants of the famous 'X-ogen' line carrier HCO + – have been observed for the first time using two cryogenic 22-pole ion trap apparatus (FELion, Coltrap) and two different light sources: the Free Electron Laser for Infrared eXperiments (FELIX), which was operated between 460 and 2500 cm − 1 , and an optical parametric oscillator operating near 3200 cm − 1 ; signals from both experiments were detected by infrared predissociation action spectroscopy. The majority of vibrational fundamentals were observed for both ions and their wavenumbers compare very favourably with results from high-level anharmonic force field calculations performed here at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations, CCSD(T). As the action scheme employed here probes the Ne-tagged weakly bound variants, Ne–HC 3 O + and Ne–HC 3 S + , corresponding calculations of these systems were also performed. Differences in the structures and molecular force fields between the bare ions and their Ne-tagged complexes are found to be very small. [ABSTRACT FROM AUTHOR]

The carbon chain ions HC 3 O + and HC 3 S + – longer variants of the famous 'X-ogen' line carrier HCO + – have been observed for the first time using two cryogenic 22-pole ion trap apparatus (FELion, Coltrap) and two different light sources: the Free Electron Laser for Infrared eXperiments (FELIX), which was operated between 460 and 2500 cm − 1 , and an optical parametric oscillator operating near 3200 cm − 1 ; signals from both experiments were detected by infrared predissociation action spectroscopy. The majority of vibrational fundamentals were observed for both ions and their wavenumbers compare very favourably with results from high-level anharmonic force field calculations performed here at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations, CCSD(T). As the action scheme employed here probes the Ne-tagged weakly bound variants, Ne–HC 3 O + and Ne–HC 3 S + , corresponding calculations of these systems were also performed. Differences in the structures and molecular force fields between the bare ions and their Ne-tagged complexes are found to be very small. [ABSTRACT FROM AUTHOR]

The surface treatment of carbon fiber/epoxy composites with a pulsed infrared (1064 nm wavelength) nanosecond (7 ns pulse duration) laser has been investigated. It is found that single 1064 nm laser pulse can remove the polymer matrix from composite surface to expose the carbon fibers by expansion of the pyrolysis gas resulting from laser-induced polymer degradation. The influences of laser power density and scan strategy on matrix removal process have been studied. The bonding strength of laser processed, adhesion-bonded CFRP (carbon fiber reinforced plastic) increase with lower matrix residues on the fibers and a linear relation is found. The adhesion-bonding strength of CFRP surfaces, tested by lap-joint shear test, exceeds the strength measured for untreated and abrasion treated (SiC paper) samples. The main origin of fiber damage of the laser-treated surface is mechanical fracture rather than thermal damage as found by laser scanning confocal microscope and scanning electron microscope. The characteristic morphologies and failure modes of shear-tested surfaces are analyzed. The obvious improvement of adhesive strength is achieved by the laser-treated surfaces attributed to matrix removal and carbon fibers protruding. A 1 D model is established to describe temperature and internal gas pressure of the irradiated surface. The new laser treatment method needs less laser energy and low pulse numbers and prove the way to an efficient, low-cost surface treatment for preparation of high quality adhesion bonded CFRP components. [ABSTRACT FROM AUTHOR]

Domain structure evolution in congruent lithium niobate single crystals under multiple infrared laser pulse irradiation was studied. The structure of narrow domain rays appeared after the first pulse became denser with pulse number due to ray widening and intensive fingering, which led to increasing the domain walls density. The almost constant wall density in the central region of irradiated zone significantly increased near the zone edge. Increase in the initial crystal temperature led to decrease in the wall density. The obtained radial dependence of the wall density was attributed to computer simulated spatial distribution of the pyroelectric field. [ABSTRACT FROM AUTHOR]

The influence of multilayer assembly on protection against infrared laser light was investigated. Multilayer assembly was exposed to a pulsed laser device, Marcatex 150 Flexi, with wavelength of 10.6 μm. Marking Speed [bits.ms–1] is the influenced parameter of laser irradiation. It presents the speed of burning. Multilayer assembly was consisted of three layers of textile materials. The first layer was top layer made of aramid, glass or Basalt fabric. The second layer is middle layer made of wool fabric. The third layer is bottom layer made of cotton fabric. Temperature of multilayer assembly was measured on the top and bottom layer of sample by contactless thermometer. Multilayer assembly was analysed by scanning electron microscopy before and after laser irradiation. The temperature of the bottom layer of multilayer assembly consist of aramid-wool-cotton was 74 °C at marking speed of 40 bits.ms–1. It is the lowest temperature. It can be concluded that the multilayer assembly containing aramid-wool-cotton provided the best protection against laser irradiation. [ABSTRACT FROM AUTHOR]

Widespread commercial application of titanium dioxide nanoparticles leads to their dispersion in the environment and inevitable interaction with living organisms. Their presence necessitates the monitoring of nanoparticle interactions with plants using advanced techniques that are capable of noninvasively and sensitively estimating the changes involved in the biochemical profile. The current study aims to investigate the effects of titanium dioxide nanoparticles on biochemicals of wheat leaves using label free, nondestructive, rapid, sensitive, and advanced spectroscopic probes: laser induced fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy coupled with multivariate analysis. The fluorescence and infrared spectra of control and titanium dioxide nanoparticle treated wheat leaves were acquired in the region from 400 to 800 nm and 4000 to 485 cm−1. The treatment of titanium dioxide nanoparticles decreases the chlorophyll content and the concentrations of cellulose, hemicellulose, xyloglucans, pectin, and lignin indicating interferences in the biosynthesis and structure of cell walls of the wheat leaves. The level of amide I, carbonyl, and methylene groups also increases following the treatment of titanium dioxide nanoparticles indicating lipid and protein peroxidation and the accumulation of carbonyl compounds. The changes in the integrated area ratios of the amide II/amide I, carbonyl/methyl, and methylene/amide II bands demonstrate disorder in the membrane integrity. This study establishes the efficiency of noninvasive, label-free, and rapid protocols based on attenuated total reflectance Fourier transform infrared and laser induced fluorescence to monitor the interactions of nanoparticles with plants at early stage of plant growth before visual signs of toxicity appear. [ABSTRACT FROM AUTHOR]

We present an ab initio study of quantitative extraction of the time-frequency spectra of multiple rescattering processes of the electrons driven by the mid-infrared laser field in a high-order harmonic generation (HHG). The HHG is calculated by solving the three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. We extend a synchrosqueezed transform (SST) technique to extract the individual contributions of multiple rescattering processes in HHG. Combining with an extended semiclassical analysis and the SST time-frequency spectrum, the role of quantum trajectories in multiple rescattering processes in HHG is clarified. We find that the SST allows us to distinguish the individual contribution of multiple rescattering processes in HHG and show the details of the spectral and temporal fine structures of the HHG, which provides an important tool for a deep understanding to the dynamics of multiple rescattering processes in HHG. [ABSTRACT FROM AUTHOR]

PM-355 is a class of polymeric solid-state nuclear track detectors which has a lot of applications in several radiation detection fields. Samples from sheets of PM-355 have been exposed to infrared (IR) laser fluences ranging from 1 to 12.8 J/cm2. The effect of IR laser radiation on the structural properties of PM-355 has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that the samples exhibit chain scission under the effect of laser irradiation up to 4.2 J/cm2, thus producing free radicals that led to the formation of new bonds started and continued until 12.8 J/cm2. This reduces the ordering structure, giving the PM-355 polymer more resilience. In addition, the laser irradiation at the fluence range 4.2-12.8 J/cm2 led to a more compact structure of PM-355, which resulted in an improvement in its isotropic nature with an increase in Vickers hardness and refractive index. Further, the color changes due to laser irradiation were computed using the transmission data in the wavelength range of 370-780 nm. It is found that the color intensity, which is the color difference between the irradiated samples and the non-irradiated one, increases with increasing the laser fluence, largely depending on the proportions of the blue color component. [ABSTRACT FROM AUTHOR]

Low-level lasers are widespread in regenerative medicine, but the molecular mechanisms involved in their biological effects are not fully understood, particularly those on DNA stability. Therefore, this study aimed to investigate mRNA expression of genes related to DNA genomic stability in skin and skeletal muscle tissue fromWistarrats exposed to low-level red and infrared lasers. For this,TP53(Tumor Protein 53) andATM(Ataxia Telangiectasia Mutated gene) mRNA expressions were evaluated by real-time quantitative PCR (RT-qPCR) technique 24 hours after low-level red and infrared laser exposure. Our data showed that relativeTP53mRNA expression was not significantly altered in both tissues exposed to lasers. ForATM, relative mRNA expression in skin tissue was not significantly altered, but in muscle tissue, laser exposure increased relativeATMmRNA expression. Low-level red and infrared laser radiations alterATMmRNA expression related to DNA stability in skeletal muscle tissue. [ABSTRACT FROM AUTHOR]

A novel method of soft ionization aerosol mass spectrometry (AMS), bipolar near-infrared laser desorption/ionization AMS (BP-NIR-LDI-AMS), has been developed for the on-line, real-time analysis of organic aerosols. Use of a single NIR laser pulse to desorb/ionize aerosols deposited onto an aluminum probe results in minimal analyte fragmentation to produce exclusively intact pseudomolecular ions at [M–H]−for acidic organic analytes and [M+H]+for basic organic analytes. Incorporation of a bipolar mass spectrometer with the NIR-LDI source enables simultaneous detection of acidic and basic species in organic particles. Limits of detection (total particulate mass sampled) for amino acids common to the organic fraction of atmospheric aerosols ranged from 69.1 pg for ornithine to 197 pg for serine on the positive channel, and from 17.0 pg for glycine to 100 pg for ornithine on the negative channel. From studies of the laser energy dependence of the NIR-LDI mechanism, it was found that [M–H]−formation for oleic acid proceeds through simultaneous action of two 1064 nm photons, suggesting a surface-assisted process rather than direct photoionization, for which photon energy is insufficient. For acidic aerosol species, sensitivity was found to increase as a function of analyte acidity, while for basic species, [M+H]+ion signals were detected only in the presence of a labile proton source, with the intensity of the ion signals scaling with the acidity of the proton source. The sensitivity of BP-NIR-LDI-AMS to the amino acids was rationalized in terms of their acidic/basic character, as measured by isoelectric point (pI), with the cationic sensitivity scaling proportionally withpIand the anionic sensitivity scaling inversely withpI. © 2016 American Association for Aerosol Research [ABSTRACT FROM PUBLISHER]

In this paper, we report results on two-colour above-threshold ionisation, where extreme ultraviolet pulses of femtosecond duration were synchronised to intense infrared laser pulses of picosecond duration, in order to study the laser-assisted photoelectric effect of atomic helium, neon, krypton and xenon which leads to the appearance of characteristic sidebands in the photoelectron spectra. The observed trends are found to be well described by a simple model based on the soft-photon approximation, at least for the relatively low optical intensities of up toemployed in these early experiments. [ABSTRACT FROM AUTHOR]

Organic salt crystals, e.g. DAST, OH1, and DSTMS, pumped by ultra-short infrared laser are efficient THz emitters. We review our latest results on the generation in organic crystals of THz single-cycle transients with field strength of 1.5 MV/cm. The energy conversion reaches 2% with photon conversion efficiency up to 200%. THz radiation produced in such crystals offers excellent beam propagation properties and can be focused down to diffraction limited spot size in order to realize the highest field. This source covers the full spectral range between 0.1 and 10 THz. Further, we discuss the possibility to control the absolute phase and the polarity of the THz field. [ABSTRACT FROM AUTHOR]

Both the physical picture of the dynamics of atoms and molecules in intense infrared fields and its theoretical description use the concept of electron trajectories. Here, we address a key question which arises in this context: Are distinctly quantum features of these trajectories, such as the complex-valued coordinates, physically relevant in the classically allowed region of phase space, and what is their origin? First, we argue that solutions of classical equations of motion can account for quantum effects. To this end, we construct an exact solution to the classical Hamilton–Jacobi equation which accounts for dynamics of the wave packet, and show that this solution is physically correct in the limit. Second, we show that imaginary components of classical trajectories are directly linked to the finite size of the initial wave packet in momentum space. This way, if the electronic wave packet produced by optical tunnelling in strong infrared fields is localised both in coordinate and momentum, its motion after tunnellingipso factocannot be described with purely classical trajectories – in contrast to popular models in the literature. [ABSTRACT FROM AUTHOR]

George Stout investigated radiation ablation as a means of erasing white paint stripes (applied to facilitate realignment) from Philae Temple sandstone blocks after their reassembly on the island of Agilkia. Forty-two years ago state-of-the-art laser technology offered very few options in terms of diversity in wavelengths and pulse lengths. Laser divestment in art conservation had only been demonstrated for black sulfate encrustations on white calcareous stones. However, a CO2 IR (10.6 µm) TEA laser from an inertial-confinement thermonuclear fusion program was available and had been employed to ablate white tufa deposits from brown Cyprian pottery shards. Consequently, Stout adapted the heat-transfer analytical modeling of a concurrent laser divestment project in Venice to white paint upon brown sandstone, characterizing the Philae situation to guide TEA-laser divestment tests on the white-striped Isis stones. In contrast to results obtained with radiation from Nd:YAG, Nd:glass, and ruby lasers, the mid-infrared radiation from the TEA laser yielded clean ablation of the white paint from the sandstone: free of etching, discoloration, or paint-ash residues. This favorable outcome was consistent with Stout's heat-transfer calculations and was evidently a consequence of both the thermal and optical properties of the paint and the Philae stones. Whereas far more versatile laser systems are now available, the Philae experiment did reveal the potential of self-limiting radiation divestment in the damage-free removal of refractory coatings of high albedo. This article presents a historical account of these early experiments with laser divestment. [ABSTRACT FROM AUTHOR]

Acne vulgaris is a common condition which remains challenging to treat in some cases. Laser and light-based therapies offer an alternative to medical therapies with the advantage of high compliance and relatively low side-effect profile. Light-based therapies in acne exert their effects through photochemical, photothermal, or a combination of both mechanisms. This article explains the mode of action for each light-based modality and examines the current evidence in this field. [ABSTRACT FROM AUTHOR]

The operating range of lean-burn spark-ignition (SI) engines is limited by the cycle-to-cycle variability of the fuel concentration at or near the spark plug at ignition timing. An experimental investigation was undertaken to measure the temporal and spatial distribution of hydrocarbon (HC) concentration in a spark-ignition engine, using the infrared (IR) laser absorption at 3392 nm. The purposes were to establish whether there is a correlation between time-resolved HC measurements for a range of global air-to-fuel (A/F) ratios (A/F = 15.5–23) with the strength of the firing stroke and to establish how this varies with fuel port-injection strategies against either open (injection timing 30° crank angle (CA) after intake top dead center) or closed-valves (injection timing 180°CA after intake top dead center), respectively resulting in stratified and near-homogeneous charge distributions. The results showed that IR line-of-sight (LOS) averaged A/F ratio measurements yielded a good agreement with the global A/F ratio readings obtained by the linear air-to-fuel (LAF) zirconia-based sensor. Furthermore, the cyclic variability of the measurements of the fuel concentration increased with increasing A/F ratio. At A/F = 23, closed-valve injection strategy resulted in small spatial stratification of the fuel charge with an ensemble-averaged correlation coefficient of fluctuations of the IR LOS A/F ratios with fluctuations of peak in-cylinder pressure of 0.37. For open-valve injection strategy, which resulted in axial fuel mixture charge-stratification but no radial charge-stratification, a maximum correlation coefficient of the IR LOS A/F ratios with fluctuations of peak pressure of 0.34 was measured (at the measurement location closest to the spark). This correlation was reduced to 0.17 at locations furthest from the spark plug. Finally, results showed that at A/F = 23, fuel stratification can be used to control lean-burn SI combustion, while at A/F = 15.5, no significant difference was observed between the two injection timings. The consequences of these findings on the fuel distribution in the pentroof and the control of the lean limits of SI engines are discussed. [ABSTRACT FROM AUTHOR]

Liquid-assisted laser ablation technique has become an alternative method to reduce the thermal damage of work material induced by a laser. In this study, water and ethanol were employed as the liquid to aid the laser grooving of polymethyl methacrylate (PMMA) sheet. The whole workpiece was submerged in the liquid and ablated under the different laser powers. A clean and deep groove can be fabricated when the PMMA was machined in the ethanol, while the ablation in water can introduce the smallest heat-affected zone compared to the air and ethanol environments. To realize the laser grooving performance, the ablation models were also developed for the first time in this study. [ABSTRACT FROM PUBLISHER]

Formation of nanodomain structures during cooling after pulse heating by infrared laser has been studied in congruent lithium tantalate (CLT) and lithium niobate (CLN) single crystals.In situstudy of the domain structure evolution allowed to reveal that in CLN the isolated domains appeared at the edges of the irradiated zone and grew to the center. In contrast, the quasi-regular stripe domain structure appeared in CLT near the edge of irradiated zone. The difference has been attributed to lower Curie temperature and larger pyroelectric coefficient of CLT. The self-organized domain structures can be used for periodical poling with submicron periods. [ABSTRACT FROM AUTHOR]

Liquid-assisted laser machining processes are of significance in the thermal damage reduction of cut material. However, the processes suffer the poor cut quality due to the disturbance of water to the laser beam. This article firstly proposes a new technique to remedy problems found in the general underwater laser ablation method. An overflow system was incorporated in the laser machining process for introducing a uniform water layer with a steady flow on the workpiece surface. By implementing this new technique, a better cut surface quality than that obtained from dry and typical underwater laser approaches can be accomplished. It is apparent that this technique could make the normal pulse infrared lasers feasible for processing materials with low thermal damage. [ABSTRACT FROM AUTHOR]

Ultra-wideband microwave-modulated laser radar is designed and fabricated for the improvement of spatial resolution both in the range and in the azimuth directions. The frequency modulation (1–18?GHz chirp) is applied to an infrared laser source in 1550?nm wavelength. A prototype of laser radar system with a beam expander has been constructed and applied to the measurement of the distance (position) of an object. In the experiment, it has been proved that the spatial resolution in the range direction is less than?±2?cm. [ABSTRACT FROM AUTHOR]

The frequency of the transition between the 3dσ GK1Σ+g(v=1,N=1) state of H2and theRydberg state belonging to a series converging to theX+2Σ+g(v+=0,N+=1) ground state of ortho H+2has been measured with an accuracy of 1.2 MHz using a narrow-band pulsed near-infrared (NIR) laser. Systematic errors originating from ac and dc Stark shifts, from pressure shifts and from the frequency shift and chirp accompanying the generation of the NIR laser pulses were quantified. By combining this frequency with the binding energy of the 56p (N= 1,S= 0) Rydberg state, the ionisation energy of theGK1Σ+g(v=1,N=1) state of ortho H2was determined to be 379855188.3(12) MHz [12670.60522(4) cm−1]. This new result represents the first step towards the determination of the ionisation and dissociation energies of molecular hydrogen at a ν/Δν level of accuracy beyond 1010. Using the current value of the ionisation energy of ortho H2[124357.23797(36) cm−1, from Liuet al.[J. Chem. Phys.130, 174306 (11)] and the frequency interval between theN= 1 andN= 0 rotational levels of theX (υ = 0) ground state of H2[118.48684(10) cm−1, from Jenningset al.[J. Mol. Spectrosc.126, 19 (28)], the term value of theGK1Σ+g(υ=1,N=1) state was determined to be 111805.1196(4) cm−1. [ABSTRACT FROM AUTHOR]

We report a high pressure Raman study of orthorhombic elemental sulfur from ambient pressure to ∼ 25 GPa. Using a near infrared laser and low laser intensity on the scattering volume, we achieve off-resonant conditions up to larger pressures in comparison with previous studies. Raman spectra were recorded over the full spectral range including external (librational, translational) and internal (bond bending and bond stretching) modes. Drastic changes are observed as regards the peak frequencies, relative intensities and band splitting of degenerate modes. The main outcome of the present study is the observation of a “structural” transition at ∼ 16 GPa manifested as slope changes of certain frequencies and sudden relative intensities changes. The present findings are discussed in the context of previous pressure Raman studies and comparison with existing X-ray diffraction as well asab initiomolecular dynamics results is attempted. [ABSTRACT FROM AUTHOR]

IR-induced elasto(piezo)-optical (PO) triggering effects in complex chalcogenide glasses with general formula Sb2Se3-xTex−BaCl2–PbCl2(withx= 0.2, 0.8, 1.3) were found under the influence of a pulsed 190 ns CO2laser with wavelength 10.6 μm. It was shown that increasingxleads to an increase of the PO efficiency. This is caused by appearance of enhanced excited dipole moments due to variations of polarizability. Simultaneously variations of the PO versus pump–probe delay times in the nanosecond time range were explored. A substantial role of the electron–phonon subsystem in the observed IR-induced PO triggering is demonstrated. The investigations were done both for diagonal as well as off-diagonal PO tensor components. [ABSTRACT FROM AUTHOR]

Results of the growth and annealing processes of Ho3+:CaNb2O6 crystal with high oxygen defects were reported. The spectroscopic properties of Ho3+:CaNb2O6 were also analysed, and the decay curves of the bulk and powder samples in correspondence with the emission 5I7→5I8 at 2·0 μm were recorded. The effects of radiative trapping on the final results were also indicated, and the final value of the fluorescence lifetimes of 5I7→5I8 transition is calculated to be 5·19 ms. CaNb2O6 crystal was shown to be a prospective material for an infrared laser medium at 2·0 μm. [ABSTRACT FROM AUTHOR]

Hailey–Hailey disease (HHD), also known as benign familial pemphigus, is an autosomal dominant skin condition that affects the adhesion of epidermal keratinocytes. Although the initial manifestation of flaccid vesicles on erythematous or normal skin in flexure sites frequently goes unnoticed, large, macerated, exudative plaques of superficial erosions with crusting are observed at the time of diagnosis. There is no specific treatment for HHD, and most cases are symptomatically supported. However, infrared laser ablation has been somewhat helpful. We present a case successfully treated with fractional CO2laser showing a long-term favourable outcome and no adverse effects. Thus, this modality could be an alternative to full ablation for this condition. [ABSTRACT FROM AUTHOR]