A. A. Chistyakov

Ion formation upon water excitation by IR laser radiation in the range of OH stretching vibrations

The ion formation and emission upon the excitation of liquid water in the range of OH stretching vibrations were observed and studied. The radiation source was a nanosecond parametric light oscillator tunable in the range of 2.7–3.3 μm. The ions were detected by an ion-mobility spectrometer.

Photophysical processes stimulated in nanoporous silicon by high-power laser radiation

Photoprocesses initiated on the surface of porous silicon irradiated with laser radiation with wavelengths (λ = 266, 337, and 532 nm) in a wide range of intensities (up to 2 × 107W/cm2) were investigated. Laser-induced luminescence and laser mass-spectrometry were used as experimental procedures. X-ray reflection was used to determine the parameters of the porous silicon films. The photoluminescence spectra obtained at different wavelengths and low intensities were analyzed. This analysis showed that for an optically thin layer of porous silicon the luminescence spectrum does not depend on the wavelength of the exciting radiation. This indicates the existence of a separate system of levels in porous silicon that are responsible for the luminescence. The behavior of the photoluminescence spectra as a function of the intensity q of the exciting radiation was investigated. It was shown that the luminescence intensity is a nonlinear function of q. At high intensities of the exciting radiation, the luminescence intensity saturates and a short-wavelength shift of the spectra is observed; this is due to the high concentrations of photoexcited carriers. This increases the probability of the experimentally observed nonequilibrium photodesorption of H2 and Si from the surface of porous silicon.

Resonant radiationless excitation transfer to I2 molecules sorbed in pores of porous silicon

Resonant radiationless electronic excitation transfer to I2 molecules sorbed in pores of porous silicon was observed. The mass-spectrometry technique was used to show that iodine excitation through the resonant transfer results in the desorption of sorbed I2 molecules with relatively high kinetic energies (1−3 eV).

Photoprocesses on a surface of nanoporous quartz under resonant laser radiation

The photoexcitation of iodine molecules on surfaces of solid (nonporous) and nanoporous quartz by resonant laser radiation in the visible region has been studied. We have detected and studied the high-energy photodesorption of iodine molecules with a translational energy of 1.4 to 1.8 eV from nanoporous quartz surfaces at an exciting photon energy ranging between 1.9 and 2.3 eV, as well as the nonequilibrium surface dissociation of molecules. Unlike the photoprocesses, which are observed only on the surface of nanoporous quartz, the thermal desorption of I2 molecules with a considerably lower kinetic energy has also been detected on the surface of solid quartz. We have suggested a physical mechanism of photodesorption, under which electronic excitation of an iodine molecule in the confined volume of a nanopore is accompanied by a Franck-Condon electronic transition of a molecule-surface complex to a state with a higher potential energy and subsequent release of this energy in the form of kinetic energy. It has been concluded that photoprocesses on a nanostructured surface are radically different from ordinary surface photoprocesses.