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The behavior of a thin-film GeTe crystal induced by intense femtosecond laser pulses ( μm) has been studied using a pulsed electron diffractometer. The sample is an annealed 20-nm GeTe film on a copper grid with a carbon coating. It has been found that laser ablation results in the formation of an ultrathin GeTe crystal (assumingly, GeTe monolayer) with a high radiation resistance. Possible reasons for the detected nanosize effect are discussed. [ABSTRACT FROM AUTHOR]

The coherent lattice dynamics in thin crystalline Sb and Bi films has been investigated using ultrafast electron diffraction. The samples were exposed to Ti:sapphire femtosecond laser radiation and probed by ultrashort electron pulses. The registered generation of coherent optical phonons in the crystals corresponded to the A1g and Eg modes and their combinations in Sb, as well as to the manifestation of the A1g mode and its first and second overtones in Bi. Detection of optical phonons with frequencies of up to 9 THz indicated that a temporal resolution at a level of ~100 fs was obtained. An ultrafast electron diffractometer for studying nonlinear laser-induced processes in molecular and cluster beams has been developed based on a femtosecond electron source. [ABSTRACT FROM AUTHOR]

Direct methods of imaging of the substance that was excited by a femtosecond laser in the space–time continuum, which are based on the sensing of the sample by ultrashort electron bunches, strictly synchronized with femtosecond laser pulses, have been demonstrated. A number of experiments in the field of ultrafast electron microscopy and diffraction performed at the Institute of Spectroscopy of the Russian Academy of Sciences has been presented. [ABSTRACT FROM AUTHOR]

The modification of a graphene sheet, which was fabricated by chemical vapor deposition on a close-meshed copper grid, during powerful femtosecond laser irradiation is studied. The process of long-term irradiation of a sample in vacuum is found to be accompanied by (1) breaking carbon bonds, which is indicated by a decrease in the intensities of the reflections corresponding to electron-beam diffraction by graphene and (2) the formation of new products, which is indicated by the appearance of new diffraction rings and a change in the Raman spectrum of the sample. The compositions of the forming chemical compounds are analyzed. Copper oxides Cu2O and CuO are shown to form predominantly on the sample surface as a result of the chemical reactions induced by powerful femtosecond laser pulses. [ABSTRACT FROM AUTHOR]

The excitation and ionization of CFI molecules and their clusters by femtosecond UV laser pulses is studied. It is concluded that the types of excitation of free CFI molecules and their clusters by femtosecond UV laser pulses are different. The composition and kinetic energy of ion products observed upon the ionization of (CFI) clusters by femtosecond pulses are found to differ considerably from those obtained upon ionization by nanosecond pulses. It is shown that the molecular I ion is produced in reactions induced in (CFI) clusters by UV radiation. Using the pump-probe method, we found the two channels of producing I ions with characteristic times τ ≈ 1 ps and τ ≈ 7 ps. A model of the reactions under study proposed in the paper is consistent with our experimental results. [ABSTRACT FROM AUTHOR]

The dynamics of multiphoton excitation of (CF)CCO molecules has been investigated under the condition of resonant action of femtosecond infrared laser radiation on the ν vibrational mode of the C=C=O bond. It has been shown that the mode-selective excitation of this vibration occurs up to the ν = 6 level. The kinetics of the subsequent intramolecular vibrational energy redistribution from the ν mode has been measured. A value of 5 ± 0.3 ps has been obtained for the characteristic time of this process. [ABSTRACT FROM AUTHOR]

The resonant vibrational excitation of gaseous iron pentacarbonyl Fe(CO)5 by femtosecond pulsed IR laser radiation is accompanied by the deposition of microcrystals of higher iron carbonyls Fe2(CO)9 and Fe3(CO)12. It is found that microstructured iron-containing films are formed on the surface of the gas-cell windows immediately in the region of laser beam passage. The possible mechanism of film formation is considered. [ABSTRACT FROM AUTHOR]