Characteristics of structural changes in fused silica under the effect of femtosecond laser radiation in the heat accumulation regime

Structural changes induced in fused silica subjected to focused femtosecond laser radiation in the heat accumulation regime are studied. The spatial profile of the induced refractive index and the effect its amplitude has on such effects as the self-focusing of the laser radiation, and thermal and photochemical processes are investigated. Individual contributions from each of these effects are separated and their effect is described on the basis of experimental dependences for the first time. It is also shown that the use of heat accumulation regime substantially increases the induced refractive index, compared to the nonthermal regime.     

The Coherent Production of the (K +π0) System by K + Beam on Copper Nuclei at the OKA Setup

Journal of Experimental and Theoretical Physics - On the statistics of ~1.7 × 108 interactions of positively charged kaons on copper nuclei, coherent events of the K+π0 system production...     

Permalloy-copper-Permalloy sandwiches with perpendicular anisotropy axes in the magnetic layers

Layerd FeNi-Cu-FeNi structures with a mutually perpendicular orientation of the easy axes in the FeNi layers are fabricated in ultrahigh vacuum, and the physical properties of these structures are investigated: ferromagnetic resonance, quasistatic magnetization reversal, and the Faraday rotation of the plane of polarization of a light wave. Zh. Tekh. Fiz. 67, 45–48 (November 1997)     

Anisotropy time dependence of photoexcited C60 and C70 in transient grating experiments. Solvent effect

Anisotropy time dependence of photoexcited C₅₀ and C₇₀ has been measured by picosecond transient grating techniques at room temperature in various solvents. The monoexponential anisotropy decay was observed for the C₆₀ molecule and biexponential anisotropy decay was observed for the C₇₀ molecule. Both for the C₆₀ and for the C₇₀ molecules anisotropy time decay is very fast. The data obtained were analyzed in terms of the rotational reorientation of fullerene molecules in solvents. Hynes-Kapral-Weinberg theory reasonably explains the observed reorientation times of fullerenes molecules. The dielectric friction effect on the C₇₀ rotational reorientation on the short axis is reported.     

A Tr Esr study of the quenching of photoexcited dioxouranium (VI) salts by stable nitroxyl free radicals

TR ESR spectroscopy was applied to the study of the quenching of excited dioxouranium (VI) (uranyl) nitrate and sulfate by stable nitroxyl radicals of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) family. Photoexcitation of uranyl in solutions of alcohols of moderate viscosity (η = 3-10 cP) in the presence of TEMPO leads to CIDEP signals of TEMPO due to a radical triplet pair mechanism (RTPM). Polarized nitroxyls were also observed in solutions of polyelectrolyte sodium poly(styrenesulfonate), NaPSS, in the presence of the nitroxyl with a positively charged trimethylammonium group. Photolysis of uranyl salts in solutions of alcohols leads to the generation of free radicals of alcohols. No CIDEP of these radicals was observed, distinguishing U₂ ^2+* from its organic analog, the triplet benzophenone. The probable reason for the lack of polarization in uranyl photoreduction reactions is the difficult access of free radicals to the U atom of the solvated radical UO₂₊ (V); this atom bears the unpaired electron. The role of polyelectrolytes in the enhancement of the quenching of excited states is discussed. Results are in agreement with the statement that photoexcited uranyl has a triplet multiplicity.     

Photophysical properties of the extract of endometallofullerenes La@C2n inortho-dichlorobenzene. Picosecond laser photolysis

The kinetics of relaxation of optical anisotropy induced by polarized light in endometallofullerenes La@C_2n inortho-dichlorobenzene was studied by picosecond laser photolysis. Decay of the optical absorption signal due to the excited states of La@C_2n follows the biexponential law with two values of relaxation time:t ₁=35±3 ps andt ₂=1100±200 ps. The lifetimet or decay of the optical anisotropy is 19±5 ps and determined by the orientational diffusion of La@C_2n . The experimentally determined lifetime of optical anisotropy agrees satisfactorily with the value yielded by the theoretical model of orientational diffusion under slip boundary conditions at the interface of the La@C_2n molecule with the solvent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 10, pp. 1921–1923, October, 1999.