G. N. Makarov

Selective dissociation of SF6 molecules in a two-frequency infrared laser field

Abstract The dissociation of SF 6 in the field of two infrared frequencies is studied. It is shown that the selectivity of dissociation is increased compared to the single frequency dissociation case. The dispersion characteristics of the vibrational quasicontinuum have been obtained. A theoretical model of the processes is discussed.

Characteristics of multiple-photon dissociation of OsO4 molecule by two frequency tunable CO2-laser pulses

Abstract Using two-frequency technique for the multiple photon dissociation of OsO 4 molecule by IR laser radiation, the following new results have been obtained: 1. the narrow resonances of multiple photon absorption on few low lying vibrational transitions have been found in the dissociation yield as a function of exciting frequency ν 1 ; 2. the structure of the dissociation yield as a function of dissociating frequency ν 2 connected with high lying vibrational transition has been studied; 3. the kinetic of the vibration relaxation of high vibrationally excited molecules was investigated; 4. the unimolecular character of the multiple photon dissociation of OsO 4 has been proved.

Isotope-selective dissociation of the OsO 4 molecule by two pulses of infrared radiation at different frequencies

The dissociation of the OsO4 molecule in a two-frequency infrared laser field has been investigated. A twentyfold increase in the dissociation rate was obtained when the dissociation frequency was shifted to the “red” side of the linear absorption spectrum of OsO4. Osmium isotope separation was carried out by this two-frequency method. Optimal conditions for a scalable isotope separation process have been formulated.

Influence of collisions and pulse intensity on multiple photon absorption in SF6

Abstract Using a pyroelectric detector, the multiple photon absorption (MPA) of the SF 6 molecule in a wide range of pressures (10 -3 -1 torr) has been studied. The significant role of collisions in MPA has been shown. The fraction of molecules excited under essentially collisionless conditions has been defined. It is shown that under collisionless excitation of SF 6 ( p -2 torr) at energy fluences E -1 J/cm 2 the intensity of the laser pulse plays the essential role, while in presence of collisions MPA is determined mainly by the energy fluence in the pulse.

The homogeneous Lorentzian IR absorption spectrum of (CF3)3CI at twice the threshold vibrational energy

Abstract A new photodissociation method is used for studying the IR spectrum of highly excited (CF 3 ) 3 CI molecules in a beam. The dissociation yield is measured by means of resonance-enhanced multiphoton ionization of the I atom using a pulsed dye laser. The experimentally obtained IR spectrum of highly vibrationally excited (CF 3 ) 3 CI ( E =35000±2500 cm −1 ) is Lorentzian with half-width γ≈9 cm −1 . The effects of vibrational and rotational inhomogeneous broadening on the measured spectrum are shown to be small.

dissociation of the OsO4 molecule by intense IR laser pulses

Abstract The frequency dependence of the dissociation rate of the OsO 4 molecule by a strong infrared resonant field is shown to have a rich structure due to multiple photon absorption resonances. This permits laser isotope separation with small isotope shift. No dissociation was observed in the case of excitation of the R branch of the v 3 mode in OsO 4 . Threshold characteristics of the dissociation have been studied as well.

Direct measurement of population on molecular vibrational levels excited by laser radiation

Abstract A new method of measuring the population of vibrational levels of molecules is proposed. The population is determined by measuring the changes in the electronic absorption spectrum of molecules. It is shown that it is possible to excite 40% of the molecules in NH 3 by a pulsed TEA CO 2 laser. The time behaviour of the population is also discussed.

Investigation of multiple photon excitation of OsO4 by dissociation yield saturation

The multiple photon dissociation of OsO 4 molecules by IR laser radiation has been performed under the saturation of the dissociation yield. The absolute friction of the excited molecules, the excitation level and their frequency dependencies; the dissociation crossection and the frequency distribution of the excited molecules after excitation by the laser pulse have been obtained on the basis of these measurements. Some main features of the multiple photon dissociation of OsO 4 following from the obtained characteristics are discussed.

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.

High-power IR laser-induced acceleration of SF6 molecules in a secondary pulsed molecular beam

Abstract The method of producing of an intensive secondary pulsed molecular beam of controlled kinetic energy with high-power IR laser is suggested. The experimental results on CO 2 -laser-induced acceleration of SF 6 molecules in a secondary beam are presented. The intensive (more or equal to 10 20 molecules/str s) molecular beams of SF 6 with kinetic energy of about 1.5 eV without a carrier gas and about 2.5 and 2.7 eV with carrier gases He (SF 6 /He=1/10) and H 2 (SF 6 /H 2 =1/10), accordingly, were obtained.