V. M. Krivtsun

Diode laser study of IR multiphoton-induced depletion of rotational sublevels of the ground vibrational state of SF6 molecules cooled in a pulsed free jet

Abstract A pulsed frequency tunable diode laser was used to investigate the IR multiphoton-induced depletion of rotational sublevels of the ground vibrational state of SF6 molecules cooled in a pulsed free jet at exciting energy densities between ≈10-2 and 2.3 J cm-2. The depletion of all rotational sublevels was effective at considerable (≈5–11 cm-1) pumping frequency detunings from the linear absorption spectrum (LAS) of the molecule the width of which under the conditions of experiment (Trot ≈ 18 K) was ≈2–3 cm-1. The fraction of molecules excited by a pumping pulse from individual rotational sublevels was measured and its dependence on the exciting pulse frequency and energy density investigated. The effect of collisions on the depletion of the rotational sublevels was studied.

Ir absorption spectrum of CrO2Cl2 molecules for high-lying states of the vibrational quasi-continuum

Abstract A new approach to the spectroscopy of highly excited vibrational states of polyatomic molecules has been elaborated. The molecules of CrO 2 Cl 2 were prepared in states with a vibrational energy of the ground electronic term A 1 of ≈ 19000 cm −1 by means of internal conversion of electronic energy from the electronic state B 1 excited by laser radiation. The spectroscopy of the vibrationally excited molecules has been carried out in the region of the ν 6 and ν 1 bands with diode and CO 2 lasers. The fwhm of the obtained spectrum was ≈ 15 cm −1 . The intermode interaction in CrO 2 Cl 2 has been theoretically analyzed, and the calculated spectrum compared with that measured experimentally. The time evolution of the spectrum of vibrationally excited CrO 2 Cl 2 molecules has been studied. The average energy transferred per one collision with unexcited CrO 2 Cl 2 molecules was equal to 〈δ E 〉 ≈ 1200 cm −1 .

SPECTROSCOPIC INVESTIGATIONS WITH PULSED PB-SALT DIODE LASERS

Abstract A review of recent works made in the Diode Laser Spectroscopy Group of the Institute of Spectroscopy in Troitsk, Russia, is presented. The qualitative modifications of the rovibrational energy level structure under rotational excitation (so called critical phenomena) were studied for the v 1 , v 3 bands of SnH 4 and the v 3 band of the CF 4 molecule. The parameters of molecular supersonic jets have been determined for various pulsed valves. The dynamics of collisionless SF 6 and NH 3 molecules excitation by TEA CO 2 laser radiation were investigation. Possibilities of intracavity detection of molecules by means of pulsed diode lasers with an external resonator have been analyzed.

Determination of the Parameters of Condensed Media by the Dual-Wavelength Differential Absorption Method

A method of dual-wavelength differential absorption with the use of diode lasers is proposed. The method makes it possible to detect changes in parameters of media that cause broad absorption lines of selected molecular components of these media either to shift or to deform. The potentialities of the method proposed are demonstrated in experiments on remote contactless measurement of the temperature of aqueous solutions and measurement of the deviations of the composition of a mixture of dyes from the equilibrium state. These investigations show ways of increasing the sensitivity of the method proposed in solving particular experimental tasks.

Study of the NH2 radicals produced by flash photolysis of NH3

The absorption spectra of the NH2 radical have been recorded with a resolution of 10-3 cm-1 in the 1343 - 1605 cm-1 range. The formation of the radicals took place as a result of pulsed photolysis of NH3 in the 190 - 220 nm region. The total number of NH2 radicals formed was 1017 - 1018 for a 5 microsecond(s) ec duration of the photolyzing pulse and a 250 J energy supplied to the photolysis lamp. Nineteen lines of vibrational-rotational transitions with N -4 cm-1.