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A comparative study of the dispersion of nonlinear absorption in thin films of molecular J- and H-aggregates of polymethine dyes was performed with the use of the Z-scan (Z-scan technique) over the range 625–825 nm under conditions close to resonance absorption at nanosecond duration of excitation. The measurements were made on film samples of J- and H-aggregates prepared by spin-coating and having identical absorption spectra. The H- and J-aggregates were formed by the synthetic thioflavylium DT-3 and benzothiazole BTC18H dyes, respectively. It was found that the samples of different types of aggregates exhibit nonlinear susceptibility of the same order of magnitude with allowance for the width of exciton absorption peaks. [ABSTRACT FROM AUTHOR]

A number of new peaks close to the previously predicted energies of virtual electronic states [S.G. Ovchinnikov and V.N. Zabluda, Zh. Eksp. Teor. Fiz. 125, 150 (2004) [JETP 98, 135 (2004)]] have been observed in the absorption spectra of FeBO3 single crystals in the infrared range. The 0.27-eV peak was absent in the scheme presented in the work cited above and, to explain it, a multielectron theory taking into account the 2 T2 low-spin term of the Fe3+ ion has been developed. [ABSTRACT FROM AUTHOR]

Ni–P/AAO nano-array composite structure assemblies with Ni and P grown in the pores of anodic aluminum oxide (AAO) membranes were prepared by electroless deposition. The results of SEM, TEM and SAED show that as-deposited Ni–P nanowires have an amorphous structure and a few nanocrystallites form after annealing. The optical absorption spectra reveal that, as the annealing temperature increases, the absorption band edge of the Ni–P/AAO composite structure is obviously blue shifted, which is attributed to a decrease of the internal pressure after heat treatment. Meanwhile, the annealed Ni–P/AAO nano-array composite structure exhibits the absorption behavior of a direct band gap semiconductor. Details of this behavior are discussed together with the implications for potential device applications. [ABSTRACT FROM AUTHOR]

Results of spectral studies of human liquor aimed at determining the specific features of its composition arising as a result of neurosurgical diseases and during the recovery period are presented. A method for detecting characteristic bands attributed to pathology, which is based on precision measurements of the UV-VIS absorption spectra of liquor and on their subsequent computer analysis is presented. With this method, ironcontaining components of liquor can be qualitatively and quantitatively determined, which is important in solving neurosurgical problems. [ABSTRACT FROM AUTHOR]

Organic–inorganic nanostructured hybrids based on N, N′-diphenyl- N, N′-bis(3-methylphenyl)-(1,l′-biphenyl)-4,4′-diamine (MTPD) and anatase TiO2 were prepared via layer-by-layer deposition method. The MTPD/TiO2 hybrids were characterized by UV–Vis absorption spectra, photoconductivity measurements, and surface photovoltage spectra (SPS). Due to the change of the aggregated structure caused by the addition of TiO2, MTPD showed blue-shifted absorption spectrum. The photosensitivity of MTPD/TiO2 nanostructured hybrids was increased by two times when compared with that of its single component. Studies on the SPS revealed that the efficient light-induced charge separation and transfer between MTPD and TiO2 was responsible for the improved photosensitivity. The MTPD/TiO2 hybrids exhibited high photosensitivity to ultraviolet light with weak intensity and acceptable stability under ultraviolet radiation, which endow the hybrids potential applications in the field of ultraviolet photodetection. [ABSTRACT FROM AUTHOR]

The effect of optical feedback noise of a laser diode on the stability of gas-absorption spectra was investigated by monitoring the optical absorption of CO2 gas. Lasing longitudinal mode instability greatly degraded the shape of the absorption spectra, and coherence collapse in the laser diode greatly broadened the spectra. The correlation between the optical feedback noise of the laser diode and the shape of the gas-absorption spectra was clarified on the basis of these spectral behaviors. [ABSTRACT FROM AUTHOR]

A direct quantum-mechanical calculation of the intensity distribution in the two-photon absorption spectrum of benzonitrile is performed taking into account the Herzberg-Teller effect. The excitation mechanism of all the observed lines, including lines corresponding to the excitation of single-quantum nontotally symmetric vibrations and their combinations with totally symmetric modes, is analyzed. The results of the calculation, performed taking into account the frequency effect and the Duschinsky effect, agree satisfactorily with experimental data. This indicates that it is worthwhile to apply the quantum-mechanical method in calculations of the intensity distribution in the two-photon absorption spectra of cyclic molecules. [ABSTRACT FROM AUTHOR]

The fundamental absorption edge of the gadolinium trihydride has been studied by performing optical transmission measurements at temperatures ranging from 298 K to 353 K. Urbach tails and the photon absorption spectra give information about the exciton dynamics, distinguishing between free and trapped excitons in the lattice. Our experimental results can be accounted for in terms of the theory of Toyozawa and co-workers, which ascribe the Urbach tail to the momentary localization of excitons due to phonon interaction. [ABSTRACT FROM AUTHOR]

A quantum-chemical analysis of the donor-acceptor properties of a C60 + dimethylenemethylamine binary system is performed. It is shown that the term of the intermolecular interaction is two-well, because of which the optimization of the system structure at the initial distances between the molecules of 0.21 nm or smaller leads to the formation of N-methylfullerenepyrrolidine C60. At initial distances exceeding 0.25 nm, a weakly bound charge transfer complex with almost complete retention of the properties of the individual molecules is formed. The low-temperature emission and absorption vibronic spectra of N-methylfullerenepyrrolidine C60 in the crystalline toluene matrix are studied experimentally. It is found that the absorption spectra of the fulleroid and pure fullerene in the region corresponding to the excitation of the lowest electronic states are generally similar. The difference observed between the low-frequency spectra agrees completely with the quantum-chemical analysis performed. [ABSTRACT FROM AUTHOR]

Abstract??The equilibrium constants,K2, have been determined for the proton-transfer reactions of 1-phenacylquinolinium ion, PHQ+, with several amines {triethylamine (TEA),N,N,N?,N?-tetramethylethylenediamine (ED),N,N,N?, N?-tetramethylpropanediamine (PD),N,N,N?,N?-tetramethylbutanediamine (BD), and 1,8-bis(dimethylamino-naphthalene (DMAN)} in acetonitrile (AN), AN-tetrahydrofuran (THF) and AN-ethanol (EtOH) mixtures. The reaction was followed spectrophotometrically using a stopped-flow technique. TheK2value decreased for DMAN and increased for TEA with increasing vol-% of THF in AN-THF mixtures. The changes in theK2value for ED, PD and BD changed in the order: ED, PD and BD from a pattern similar to TEA to a pattern similar to DMAN. The change in theK2value for DMAN with increasing vol-% of THF in AN-THF mixtures was explained by the effect of polarity on the stability of P?Q+(the deprotonated product of PHQ+). The effect of THF on theK2value is consistent with that of the peak wavelength of the absorption spectrum of P?Q+. The change in theK2value for TEA, ED, PD and BD depended on the structures of the protonated bases, one of the products for this reaction. The effect of EtOH on theK2value for DMAN was examined in ternary EtOH-THF-AN mixtures that contain different amounts of EtOH and whose relative permittivities were adjusted to that of EtOH. TheK2value increased with increasing vol-% of EtOH because of the stabilization of P?Q+upon the formation of the hydrogen-bonded complex with EtOH. The absorption spectrum of P?Q+demonstrated a blue shift as the vol-% of EtOH increased. [ABSTRACT FROM AUTHOR]

According to the results of quantum-chemical and correlation studies, ionized states of Alizarin and Alizarin Red are contributed mainly by tautomeric anthraquinoid structures. The probability of their formation increases due to solvation. The experimental electronic absorption spectra of the corresponding anions contain bands typical of the 2,9-, 1,10-, and 1,2-anthraquinoid tautomers. The 9,10-anthraquinoid structure of the anions is less probable. [ABSTRACT FROM AUTHOR]

A numerical simulation has been performed, indicating that the statement on the detection of water dimer absorption by V.I. Serdyukov et al. in Pis’ma Zh. Eksp. Teor. Fiz. 89, 12 (2009) [JETP Lett. 89, 10 (2009)] had been premature. Most of the revealed induced absorption can be attributed to water monomers. [ABSTRACT FROM AUTHOR]

The behavior of the spectral position of the absorption band of colloidal silver in photochromic glass is analyzed in relation to the variation in the refractive index of a thin layer of the medium (shell) that surrounds silver nanoparticles. It is shown that the appearance of a shell with a high refractive index leads to a long-wavelength shift in the plasmon absorption band of silver nanoparticles. These results make it possible to explain particular features of the absorption spectrum of photothermorefractive glasses. [ABSTRACT FROM AUTHOR]