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Charge migration during light–matter interaction is one of the most fundamental processes which plays a key role in chemical and biological processes of molecule. The measurement of this process requires the extreme temporal and subatomic spatial resolutions. Here, we show that a scheme based on infrared pump and short extreme ultraviolet probe technique enables us to trace the laser-controlled electron motion with high spatiotemporal resolution. By numerically solving the time-dependent Schrödinger equation for combined with a simple double-slit model, we demonstrate that the laser-controlled charge migration can be directly reconstructed from the interference patterns of the photoelectron spectrum. [ABSTRACT FROM AUTHOR]

Nonlinear metasurfaces provide a promising platform for integrated nonlinear photonic devices owing to their unprecedented capability of nonlinear wavefront manipulation. However, the previously reported second‐harmonic (SH) metasurfaces are mainly based on the nonlinear Pancharatnam–Berry phase modulation. While this method is quite convenient and robust, it shows limitations of modulation efficiency and the difficulty in extending to multidimensional combined modulations. Here, the resonant nonlinear synthetic metasurface is proposed and experimentally demonstrated for independent phase and amplitude modulations of the SH beam. A high SH modulation efficiency of 75% (with a theoretical limit of 90%) is achieved in the polarization‐dependent SH metalens. Moreover, SH holographic imaging with phase and amplitude (at 2 and 4 levels) combined modulation is realized experimentally. Compared with the pure‐phase modulation, the signal‐to‐noise ratios are increased by 2 and 3 times when 2‐ and 4‐level amplitude controls are introduced. This is not only an important step in the improvement and innovation of holographic display technology, but also paves a distinct avenue toward multifunctional, higher efficiency, and ultracompact nonlinear optical devices. [ABSTRACT FROM AUTHOR]

We theoretically investigate the high-order harmonic generation (HHG) driven by dual-pulse lasers. The first pulse of 800 nm can create plasma in the high-density gas target. Then, the second pulse of 1800 nm is spatiotemporally reshaped by the plasma and generates soft x-ray high-order harmonics in the overdriven regime. The simulation results show that adding the first pulse can promote the phase matching of HHG in the cutoff region. As a result, a cutoff-extended HHG is achieved, which is one order of magnitude more intense than that in one pulse scheme reported previously. In dual-pulse driving lasers, the harmonic yield and the cutoff photon energy can be optimized effectively by increasing the gas pressure inside the water window region. [ABSTRACT FROM AUTHOR]

An inline fiber sensor for simultaneous measurement of curvature and temperature based on anti-resonant (AR) effect combined with multimode interference (MMI) is proposed and experimentally demonstrated. The sensing structure is simply formed by embedding a section of multimode fiber (MMF) and glass capillary between single-mode fibers (SMF). Thence the multimode interference (MMI) pattern with dips and the AR effect spectrum with the loss valleys at the resonance wavelengths can be observed on the optical spectrum analyzer (OSA). A curvature sensitivity of −9.25 dB/ $\text{m}^{-1}$ with almost unchanged wavelength can be achieved by intensity demodulation at an AR valley. And a temperature sensitivity of 30 pm/°C with a tiny intensity sensitivity −0.079 dB/°C is obtained by wavelength demodulation at a MMI dip. Different demodulation mechanisms enable our sensors to discriminate curvature and temperature. Moreover, the advantages such as repeatability of fabrication, robust structure and cost-effectiveness, further benefit its practical sensing applications. [ABSTRACT FROM AUTHOR]

The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization (ATI) of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4f and 5f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale. [ABSTRACT FROM AUTHOR]

We investigate the topological edge modes in a rhombic waveguide array with imaginary coupling, which is realized by incorporating auxiliary waveguide between the coupled waveguides. By suitably tuning both real and imaginary couplings to generate an effective π flux, a non-Hermitian analog of Aharonov-Bohm (AB) cage is formed as the band structures become flat and coalesce into third-order exceptional points (EPs). We show the array can support gapped topological edge modes, which can be explained by mapping the system Hamiltonian into the square root of an anti-parity-time (PT) -symmetric waveguide array. In contrast to the linear power increase of bulk modes, the propagation of edge modes can be conserved or exponentially amplified depending on which termination is initially excited. Our study provides a promising way to realizing robust light propagation. [ABSTRACT FROM AUTHOR]

We discuss the non-dipole effect in high-order harmonic generation from atoms driving by a linearly polarized vortex beam. Different from the selection rule under the dipole approximation, where only odd high harmonics are allowed, both even and odd harmonics are generated in the vortex beam. Moreover, the polarization states of the harmonics are modulated. Elliptically polarized high harmonics can be directly generated with a linearly polarized vortex beam. We show that these non-dipole effects arise from the orbital angular momentum and spin angular momentum of the vortex beam. [ABSTRACT FROM AUTHOR]

2D organic-inorganic lead iodide perovskites hold great promise for functional optoelectronic devices. However, their performances have been seriously limited by poor long-term stability in ambient environment. Here, we perform a systematic study for the stability improvement of a typical 2D organic-inorganic lead iodide perovskite (PEA)2PbI4. The degradation of the (PEA)2PbI4 films can be attributed to the interaction with the humidity in environment, which leads to decomposition of the perovskite components. Then, we demonstrate that polymer passivation provides an effective approach for improving the crystal quality and stability of the (PEA)2PbI4 films. Correspondingly, the photoemission of the polymer-passivated (PEA)2PbI4 films has been enhanced due to the decreased trap states. More importantly, a hydrophobic polymer (Poly(4-Vinylpyridine), PVP) will protect the (PEA)2PbI4 films from humidity in ambient environment, which can greatly improve the physical and chemical stability of the 2D perovskite films. As a result, the PVP-passivated (PEA)2PbI4 films can produce a bright emission even after long-term (>15 d) exposure to ambient environment (25 °C, 80% RH) and continuous UV illumination. This work provides a convenient and effective approach for improving the long-term stability of 2D organic-inorganic lead iodide perovskites, which shows great promise for fabricating large-area and versatile optoelectronic devices. [ABSTRACT FROM AUTHOR]

By numerically solving the three-dimensional time-dependent Schrödinger equation, we theoretically investigate the dynamic interference of the hydrogen atom in intense arbitrarily polarized high-frequency XUV pulses with and without the non-dipole correction included. Our results show a clear shift of the dynamic-interference peaks in the photoelectron spectra from the linearly and circularly polarized XUV pulses, which can be attributed to the different AC Stark shifts of the ground state. The non-dipole correction for the electron–light interaction produces a similar peak shift along the propagation direction in the photoelectron momentum spectra for the linear and circular pulses. But no obvious non-dipole effect for the AC Stark shift of the ground state is identified for the light pulse with intensity around 1019 W cm−2. [ABSTRACT FROM AUTHOR]

A method to produce circularly polarized attosecond pulses with tunable helicity from CO molecule by using an unidirectionally rotating laser field is proposed. It is found that broadband harmonic supercontinuum with circular polarization can be generated from the oriented CO molecule. This enables the production sub‐100 attosecond isolated pulse with the ellipticity as high as 0.9 at the macroscopic level. Moreover, the helicity of the generated high‐order harmonics and the attosecond pulse can be tuned by adjusting the orientation of the CO molecule. This method will be beneficial for the studies on chiral‐specific dynamics and magnetic circular dichroism on an attosecond time scale. [ABSTRACT FROM AUTHOR]

We study the temporal imaging with a gradient-index (GRIN) time lens in which both dispersion and time-varying quadratic phase modulation are introduced. The lens is built by using cross-phase modulation between a signal and a parabolic pump pulse in the nonlinear optical fiber with group velocity dispersion. A general theoretical analysis of temporal imaging by the GRIN time lens is performed in detail. Compared to thin lens in previous studies, the introduction of dispersion, benefits periodic self-imaging of both time waveform and frequency spectrum for optical pulses. Interestingly, the temporal and spectral profiles of the input can be exchanged with each other periodically in the GRIN time lens. By combining the GRIN time lens with dispersive elements on both sides, the temporal waveforms of incident optical pulses can be stretched and compressed. For an input signal composed of multiple pulses experiencing different dispersions, the temporal depth imaging of the signal is realized by scanning the timing of the pump pulse applied on the lens. The study may find great applications in ultrafast optical signal processing and measurement. [ABSTRACT FROM AUTHOR]

2D organic–inorganic hybrid perovskites are promising materials for next‐generation optoelectronic devices. Nevertheless, 2D perovskites still suffer from performance‐limiting trap states and possess fundamental photophysical effects that remain poorly understood. Herein, a photoinduced trap passivation for enhanced photoluminescence (PL) in 2D hybrid perovskites is reported. Under two‐photon excitation, the PL emission of the 2D hybrid perovskites exhibits a gradual increase in intensity and lifetime, due to the photoinduced trap passivation by interacting with oxygen in ambient environment. Interestingly, the PL increase shows distinct features at the surface and in the bulk of the 2D perovskites, which can be well revealed by a photoinduced oxygen‐diffused trap‐passivation model. Moreover, the PL increase and relaxation can recycle for several times, which suggests an excellent repeatability of the photoinduced trap passivation. The photoinduced trap passivation is critical for fundamental study of light–matter interaction in 2D perovskites, and shows great promise for improving the optoelectronic responses for functional devices. [ABSTRACT FROM AUTHOR]

We extend the functionality of nonlinear photonic crystals by fabricating a structure combining a few individual optical transformations in second harmonic generation. In particular, we employed all-optical spontaneous polarization reversal in ferroelectrics to create nonlinear holograms with curved fork-like spatial modulation of nonlinearity for the generation of second harmonic optical vortices. The curved fork-like structure represents a combination of a standard vortex harmonic generator (fork structure) and an axicon, thereby allowing us to realize the second harmonic "perfect vortices" whose diameter remains constant independently of their topological charge. [ABSTRACT FROM AUTHOR]

We proposed and demonstrated a compact inline optical fiber sensor for curvature and temperature measurement with low cross sensitivity. The device consists of a 5 mm long hollow-core fiber (HCF) spliced between two single-mode fibers. Two up-tapers were fabricated at each splicing joint forming a Mach-Zehnder Interferometer (MZI). The HCF acted as the anti-resonant reflecting optical waveguide (ARROW), giving periodic dips at resonant wavelengths in the optical transmission spectrum. The cross sensitivity of curvature and temperature problem is solved by demodulating the wavelength shift of the MZI for temperature sensing and intensity variation of ARROW dips for curvature sensing. The curvature and temperature sensitivities are experimentally measured to be −4.28 dB/m−1 and 25.76 pm/°C, respectively. The cross sensitivities for ARROW is measured to be 0.0056 m−1/°C. The structure of the sensor is simple and compact, which can be used for structural health monitoring in a complex environment. [ABSTRACT FROM AUTHOR]

Experiments involving laser produced tin plasma have been carried out using a CO2 laser with an energy of 800 mJ/pulse and a full width at half maximum (FWHM) of 80 ns in vacuum. Time-integrated extreme ultraviolet spectral measurement showed that the peak of the extreme ultraviolet lithography spectrum was located at 13.5 nm and the spectrum profile's FWHM of the unresolved transition arrays was 1.1 nm. Plasma parameters of the electron temperature and density measurements in both axial and radial directions at later times had been obtained from a two-dimensional time and space resolved image spectra analysis. The axial spatial distribution of the electron density showed a 1/d2.6 decrease profile, and the radial spatial distribution of the electron density showed a 1/r1.1 profile, in which d is the axial distance from the target surface and r is the radial distance. The electron density was found to maintain symmetry across the radial distance at all delay times. Near the plasma plume center, the electron temperature Te varied slightly with increasing axial or radial distance, which was related to collisional decoupling and reheating of the ionized species in the plasma at distances longer than 3 to 4 mm. The space averaged electron temperature was measured in the range of 3.4-1.0 eV, and the space averaged electron density was measured in the range of 2.0 × 1017 to 2.2 × 1016 cm-3, as the time delay varied from 1.6 μs to 3.6 μs with respect to the pulse discharge. Time evolutions of the plasma temperature and density were found to have an apparent rise at a delay time of 2.4 μs in the corresponding time of the laser pulse tail peak. This suggests that plasma parameters and extreme ultraviolet emission intensity can be controlled by a double pulse combined laser. [ABSTRACT FROM AUTHOR]

In the fiber sensing research area, a pair of sharp contradictions is highlighted: high sensitivity and large dynamic range. In addition, the question of how to enable user-editable features for fiber optic sensors is gaining more and more attention. This letter presents a fiber acoustic sensor with real-time controllable sensitivity based on the optical vernier effect, which is possibly a solution to such a problem. The optical vernier structure with amplified and real-time tunable detection sensitivity is formed by cascading a Sagnac interferometer and a laboratory-made tunable Fabry–Perot interferometer (FPI). Sound pressure and frequency of the acoustic signal can be all-optically demodulated simultaneously by spectral reading and spectral scanning method, respectively. Experimental results show a real-time controllable acoustic sensitivity (1×, 5×, and 10× are demonstrated) and a maximum sensitivity is as high as 37.1 nm/Pa (10× of single FPI) within relatively large sound pressure range of 62.2–92.4 dB. By adjusting the FPI cavity length in real time, sensitivity can be controlled to meet the needs of different users or occasions. The proposed sensor has merits of controllable sensitivity in real time, high sensitivity, and large dynamic range, enabling the applications related but not limited to acoustic sensing. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDCs) present extraordinary nonlinearities and direct bandgaps at the K and K′ valleys. These valleys can be optically manipulated through, for example, plasmon–valley-exciton coupling with spin-dependent photoluminescence. However, the weak coherence between the pumping and emission makes exploring nonlinear valleytronic devices based on TMDCs challenging. Here, we show that a synthetic metasurface, which entangles the phase and spin of light, can simultaneously enhance and manipulate nonlinear valley-locked chiral emission in monolayer tungsten disulfide (WS2) at room temperature. The second-harmonic valley photons, accessed and coherently pumped by light, with a spin-related geometric phase imparted by a gold (Au) metasurface, are separated and routed to predetermined directions in free space. In addition, the nonlinear photons with the same spin as the incident light are steered owing to the critical spin–valley-locked nonlinear selection rule of WS2 in our designed metasurface. Our synthetic TMDC–metasurface interface may facilitate advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices. By entangling the phase and spin of light, a synthetic metasurface is shown to be able to coherently manipulate the valley-exciton-locked chiral emission in monolayer tungsten disulfide at room temperature. The findings will be of benefit to advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: The near‐field features of graphene plasmons (GPs) using a recently developed photo‐induced force microscopy (PiFM) technique are characterized here. The GPs are excited by a mid‐infrared laser beam obliquely incident on graphene suspended over a metallic grating with a dielectric spacer. The PiFM records the optical force yielded by the interaction between the electric field of GPs in the normal direction and dipoles in a metallic tip. The magnitude of the optical force is proportional to the field intensity of the GPs. By detecting the interference pattern of GPs on the grating trenches, the wavelength and propagation distance of GPs can be obtained. The PiFM technique demonstrated here provides a powerful tool to precisely characterize GPs in a deeply subwavelength scale and aid in the design of nanoscale optical devices based on graphene. [ABSTRACT FROM AUTHOR]

Abstract: The driving forces for the phase transitions of ABX3 hybrid organic–inorganic perovskites have been limited to the octahedral tilting, order–disorder, and displacement. Now, a complex structural phase transition has been explored in a HOIP, [CH3NH3][Mn(N3)3], based on structural characterizations and ab initio lattice dynamics calculations. This unusual first‐order phase transition between two ordered phases at about 265 K is primarily driven by changes in the collective atomic vibrations of the whole lattice, along with concurrent molecular displacements and an unusual octahedral tilting. A significant entropy difference (4.35 J K−1 mol−1) is observed between the low‐ and high‐temperature structures induced by such atomic vibrations, which plays a main role in driving the transition. This finding offers an alternative pathway for designing new ferroic phase transitions and related physical properties in HOIPs and other hybrid crystals. [ABSTRACT FROM AUTHOR]

Abstract: Two‐photon‐absorption‐induced photoluminescence (TPL) from nanostructures is generally inefficient since it is a typical third‐order nonlinear optical process. Herein, a hybrid dielectric structure composed of dielectric microspheres (approximately micrometers in diameter) covering a 2D perovskite flake is reported, which provides a straightforward strategy for enhancing the TPL emission. The microspheres in the hybrid dielectric structure not only concentrate the pumping laser but also effectively increase the detection efficiency of the emitted TPL signal. The internal quantum efficiency of the 2D perovskite is also increased in the hybrid dielectric structure due to a reduced nonradiative rate. These effects cooperatively increase the TPL emission by two orders of magnitude in the hybrid dielectric structure. Moreover, the hybrid dielectric structure is proven to be useful for TPL‐based superresolution imaging at a relatively low excitation power of 0.05 mW. This work demonstrates great promise for developing low‐cost, high‐performance nonlinear nanodevices based on hybrid dielectric structures. [ABSTRACT FROM AUTHOR]

We investigate the light propagation in a double-waveguide coupler with imaginary-valued coupling coefficient. The imaginary coupling is realized by incorporating an additional waveguide between the coupled waveguides and considering both gain and loss. Both symmetric and asymmetric couplers with imaginary coupling are analyzed. The coupling strength can be controlled by varying the dielectric gain and loss. As the coupling is imaginary, the energy of the system is no longer conserved and the light intensities in individual waveguides should oscillate in phase. It is also found that the exceptional points can emerge in the asymmetric couplers, which are reflected from the beat length of the intensity oscillation. The study may find great applications in optical switches and splitters. [ABSTRACT FROM AUTHOR]

Over the past decades, optical parametric amplification (OPA) has become one of the most promising sources of ultrafast Mid-IR laser, owing to its outstanding properties including ultrabroad bandwidth, superior tunability, good beam quality, and scalable energy. In this paper, we review the recent progress in ultrashort laser pulse generation via chirp manipulated OPA, which improves the energy scalability and gain bandwidth by strategically chirping both pump and seed pulses. The gain mechanism is theoretically analyzed and the OPA processes are numerically simulated. In addition, the concept is verified experimentally. Femtosecond pulses with hundreds of mJ are generated in a high energy dual-chirped-OPA (DC-OPA), and ultrabroadband μJ-level spectra supporting sub-2-cycle pulse durations are achieved in BBP-OPA. Furthermore, the obtained pulses show excellent tunability through the NIR to Mid-IR regions, which makes them a suitable seeding source for further amplification as well as powerful tools in various applications such as strong field physics, attosecond science, and ultrafast spectroscopy. [ABSTRACT FROM AUTHOR]

We investigate the surface plasmonic lattice solitons (PLSs) in semi-infinite graphene sheet arrays. The surface soliton is formed as the surface plasmon polaritons (SPPs) tunneling is inhibited by the graphene nonlinearity, and meanwhile the incident power should be above a threshold value. Thanks to the strong confinement of SPPs on graphene, the effective width of surface PLSs can be squeezed into deep-subwavelength scale of ∼0.002λ . The influence of the graphene loss on the surface PLSs is also discussed. Based on the stable propagation of surface PLSs, we find that the light propagation can be switched from the array boundary to the inner graphene sheets by reducing the incident power or increasing the chemical potential of graphene. The study may find promising application in optical switches on deep-subwavelength scale. [ABSTRACT FROM PUBLISHER]

Here we report on the hybrid nanostructures where a single ZnS nanobelt was half-covered with an aluminum (Al) film, which is an ideal platform for studying the second-harmonic generation (SHG) enhancement effects of the Al coating. It was fabricated by the lift-off process and allowed for the accurate comparison of the SHG intensity between the Al-covered and the same bare ZnS nanobelt under consistent test conditions. The results indicate that the Al coating in the hybrid nanostructures not only confines the pumping laser in the ZnS effectively, but also concentrates the emitted SHG signal greatly, increasing the signal collection efficiency. By the combination of these two effects, ∼60 times enhancement of the SHG intensity is achieved at the optimized geometry size (width and thickness) of the ZnS nanobelts. The Al-based hybrid nanostructures open up new possibilities for low-cost, highly efficient and directional coherent nanolight sources at short wavelengths. [ABSTRACT FROM AUTHOR]

We investigate the exceptional points (EPs) in a non-Hermitian system composed of a pair of graphene sheets with different losses. There are two surface plasmon polaritons (SPPs) modes in the graphene waveguide. By varying the distance between two graphene sheets and chemical potential of graphene, the EPs appear as the eigenvalues, that is, the wave vectors of the two modes coalesce. The cross conversion of eigenmodes and variation of geometric phase can be observed by encircling the EP in the parametric space formed by the geometric parameters and chemical potential of graphene. At the same time, a certain input SPP mode may lead to completely different output. The study paves a way to the development of nanoscale sensitive optical switches and sensors. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate an optical fiber sensor based on a section of silica tube fusion spliced between single mode fibers. When light is conducted into the hollow core of the silica tube, anti-resonant reflecting guidance occurs, which leads to the periodic attenuation dips in the transmission spectra of the structure. The transmission intensity of the attenuation dips can be influenced by the surrounding medium, which gives rise to the application for liquid level sensing. A liquid level sensitivity of 0.4 dB/mm is achieved by immersing the sensor head vertically into water. Experimental results also prove that such a sensor is insensitive to temperature, eliminating the requirement for temperature compensation. [ABSTRACT FROM PUBLISHER]

We propose a graphene Ramsey interferometer to study the non-reciprocal phase shift and modulation of surface plasmon polaritons (SPPs). The Ramsey interferometer is constructed by a spatially separated graphene pair that can support two SPP modes. By dynamically modulating the surface conductivity of graphene, the SPP modes will undergo uncompleted cross conversion and an additional phase shift. When adopting two modulation regions in the interferometer, the converted mode will jump back with a nonreciprocal phase shift which can be controlled by the modulation length or phase. The SPP mode of phase shift will interfere with the throughout unconverted one, resulting in arbitrary power arrangement between the two SPP modes. The study may find great applications in plasmonic isolators, phase detectors, and one-way mode converters. [ABSTRACT FROM PUBLISHER]

A multi-components interferometer based on partially filled dual-core photonic crystal fiber (D-C PCF) was fabricated for measuring temperature and strain. The partially filled D-C PCF was prepared by manual gluing method, and the cladding air holes surrounding one core were selectively filled with refractive index liquid while remaining other air holes unfilled. A multi-components interference with a large spectrum envelope and fine interference fringes was observed in the transmission spectrum. Theoretical and experimental investigations revealed that the large spectrum envelope was originated from the interference between the fundamental modes of two cores of the PCF, while the fine interference fringes were generated by the interference between the fundamental mode and higher order modes in one core that surrounded by unfilled air holes. The proposed device can be used to monitor temperature and strain simultaneously through matrix demodulation, with a high temperature sensitivity of 5.43 nm/°C. [ABSTRACT FROM PUBLISHER]

The high pressure behaviour of a cubic dense inorganic–organic framework [DABCOH22+][K(ClO4)3] (DABCOH22+ = diazabicyclo[2.2.2]octane-1,4-diium) has been systematically studied via synchrotron X-ray powder diffraction, over the range of 0–3.12 GPa. The framework [DABCOH22+][K(ClO4)3] shows a more rigid response, with a bulk modulus of 30(1) GPa and an axial compressibility of 7.6(4) × 10−3 GPa−1, compared with ZIF-8 and the dense hybrid solar cell perovskite CH3NH3PbI3. Density functional theory calculations reveal that the structural change in [DABCOH22+][K(ClO4)3] is attributed to the contraction of the KO12 polyhedra, which consequently results in the rotation of the perchlorate linkers and synergistic movement of the DABCOH22+ guest. Further extensive theoretical calculations of full elastic tensors give full mapping of the Young's moduli, shear moduli and Poisson's ratios of [DABCOH22+][K(ClO4)3], which are in the range of 31.6–36.6, 12.3–14.6 GPa and 0.2–0.32, respectively. The Young's and shear moduli of [DABCOH22+][K(ClO4)3] are larger than those of cubic MOF-5, ZIF-8 and CH3NH3PbI3. In addition, the narrow range of Poisson's ratios in [DABCOH22+][K(ClO4)3] indicates its very isotropic nature in response to biaxial stress. [ABSTRACT FROM AUTHOR]

We theoretically study the dissociation of H2+by UV laser pulses as a function of the photon energy ω of the pulse. Our results show that pronounced enhancements of the dissociation into highly excited electronic states can be achieved at some critical ω. This is found to be attributed to a consecutively resonant excitation mechanism where the population is first transferred to the first excited state by absorbing one photon and then to higher states by absorbing another one or more photons at the same internuclear distance. This study indicates that the strong coupling between the lowest two states of H2+can significantly affect the dissociation through higher lying states. [ABSTRACT FROM AUTHOR]