Conditions of the generation of subnanosecond pulses in a THL-100 laser system

The results from the generation and amplification of positively chirped pulses of 0.05 ns duration at a central wavelength of 475 nm in a THL-100 laser system are presented. It is found that the initial complex allows the generation of such radiation pulses with Gaussian intensity profiles and energies of up to 7 mJ. When such pulses with energies of 2–4 mJ are amplified in an XeF(C-A) amplifier, it is possible to achieve a saturation mode and obtain at the output laser beams with energies of up to 3.2 J. The possibility of compressing subnanosecond pulses at a wavelength of 475 nm in a compressor based on diffraction gratings is demonstrated.     

Model studies of THz-range generation via down conversion of the radiation of Ti:Sapphire lasers in LBO crystals

Results from model studies of the possibility of creating a source of high-power picosecond pulses of terahertz radiation via optical rectification and phase-matched down conversion of femtosecond pulses of Ti:Sapphire lasers in a nonlinear LBO crystal are presented. Modified Sellmeier equations are used in calculations. It is shown that the lengths of coherence for the generation of THz radiation at frequencies higher than 0.5 THz are more than 0.5 mm, allowing the technologically simple production of periodic structures. The maximum length of coherence is achieved for s–s type interactions in the XY plane. Phase-matched s–f type down conversion is possible only in the XY plane, including noncritical spectral matching conditions. Maximum efficiency can be expected for three-wave interactions with the polarization of interacting waves parallel to Z axis.     

Systematization of relaxation gas dynamics equations. A review

The phenomenological theory of relaxation gas dynamics equations is outlined for laminar flows of multicomponent reacting gases in an approximation analogous to the Navier-Stokes approximation. A system of general equations of relaxation gas dynamics including the level kinetics equations for all excited internal degrees of freedom is formulated on the basis of notions of continuum mechanics. A procedure of going over to particular cases characterized by certain relations between the relaxation times is described and examples of the corresponding closed systems of gas dynamics equations including systems containing the balance equations of the level or mode approximations for the vibrational energy levels of molecules of a gas mixture are given. A method of constructing a database of the models of the rate constants of physicochemical processes as coefficients in the source terms of the balance equations is considered.     

Efficiency of raman conversion of XeCl laser radiation in metal vapors

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 1, pp. 80–83, July, 1991.     

Mechanical degradation of gelatinized starch upon hydroacoustic treatment

Mechanical degradation of gelatinized starch upon hydroacoustic treatment in a rotary pulse installation was studied by spectrophotometry of the iodine-starch complexes and analysis of the concentrations of the terminal reducing groups. The energy efficiency of hydroacoustic and ultrasonic mechanical degradation was estimated.     

Low-Temperature Sorption–Luminescence Determination of Copper in Natural Water Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups chemically bonded to its surface extracts copper from solutions with pH 2–9 with a recovery of 99.9%; the sorption equilibration time is no longer than 5 min. Ultraviolet irradiation of wet sorbates cooled to the liquid nitrogen temperature (77 K) generates yellow–orange luminescence (_max = 585 nm), which was used as the analytical signal for the development of a procedure for the low-temperature sorption–luminescence determination of copper. The detection limit is 0.08 g per 0.1 g of the sorbent. The determination of copper is unaffected by the interference from 10⁴-fold amounts of Zn(II), Cd(II), Mn(II), Ni(II), Co(II), Ca(II), Mg(II), and Al(III); 10³-fold amounts of Fe(III); 30-fold amounts of Bi(III); tenfold amounts of Ag(I); and fivefold amounts of Cr(VI). The procedure was used for the determination of copper in natural water.