Oxygen-deficient centers decay with simultaneous formation of color centers in IR and UV grade silica glasses under KrF laser irradiation was studied. The nonexponential dependence of the ODC photodecay in silica glass on the UV irradiation dose (number of laser pulses) was observed. Postpulse long-time temporal behaviour of recombination luminescence and laser induced photoconductivity was analyzed for the two types of glasses in time scale up to 0.5 ms. Long time fluorescence tail is attributed to migration of electrons through the shallow traps before recombination and recovery of ODC. The models of postpulse recombination which can explain the observed nonexponential behaviour of ODC decay (geminal and homogeneous) are discussed. The principle part of impurities caused electron traps in the postpulse ODC recombination is shown.

V. N. Bagratashvili

S. I. Tsypina

S. S. Alimpiev

Ya. O. Simanovski

A. M. Prokhorov

A. O. Rybaltovski

UV Laser Decay of Oxygen-Deficient Centers in Silica Glasses

The delayed luminescence of Mo atoms was observed in XeCl laser excitation of Mo(CO)6 gas. The observed luminescence was explained by production of Mo Rydberg atoms under UV laser excitation of Mo(CO)6.

Yu. E. Belyayev

A. V. Dem&#39;yanenko

A. A. Puretzky

Formation and Luminescence of Molybdenum Atoms After UV Multiphoton Excitation of Gas Phase M<small.letters>o</small.letters>(CO)6

The UV laser chemistry of dimethylcadmium (DMCd) either chemisorbed at 297 K on n-type Si(100) with native oxide or physisorbed at 150 K on a photodeposited cadmium film has been studied by using mass spectrometry of desorbed species. A XeCl laser induced the heterogeneous fragmentation of these chemisorbed molecules as well as the desorption of DMCd, Cd, and CH3. The resonant absorption of a KrCl laser radiation by adsorbed DMCd led to their photolysis and the ejection of DMCd and its fragments in both neutral and ionic forms. The kinetic, laser fluence, and time-of-flight dependences of desorbed species have been measured to elucidate the mechanisms of the dissociative and desorption processes either induced by lasers or occurring spontaneously. The effects of these lasers on chemisorbed DMCd as well as KrCl laser assisted processes in chemisorbed and physisorbed molecules have been compared.

V. N. Varakin

A. P. Simonov

UV Laser Induced Chemistry of Adsorbed Dimethylcadmium

Nonlinear interaction of laser emission with a chemically reactive medium, in which a branched chain reaction may readily occur, has been analyzed aiming at essential intensification the contrast of photochemically induced phase gratings. For the model system CS2/O2, the degenerated four-wave mixing is theoretically studied under the assumption of CS2 photodissociation followed by subsequent secondary reactions induced by reactive photodissociation products. For varied CS2 concentrations and incident flux intensities, the dynamics of nonlinear reflection has been analyzed and same laser applications of such systems are suggested.

M. G. Galushkin

E. B. Gordon

M. S. Drozdov

K. A. Sviridov

Chemical Intensification of Nonlinear Multi-Wave Interactions

IR multiphoton dissociation of C4F9 COI was studied by the second-harmonic radiation of TEA CO2 laser. The stretching vibration of the carbonyl bond <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>C = O</mml:mtext></mml:mrow></mml:msub></mml:math> was excited. The second harmonic of CO2 laser was generated with the use of nonlinear crystal AgGaSe2. The maximum energy fluence at focus was &#934; &#8771; 1.2 J/cm2. The MPD of C4F9 COI was proved to be effective and selective with respect to oxygen and carbon isotopes. The main dissociation products were C4F9I and CO. The dissociation product, CO, was enriched with both 16O and 12C when the C4F9 COI molecule was excited at the center of the band <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>C = O</mml:mtext></mml:mrow></mml:msub></mml:math> by the laser line 10P (18) with 2&#969;las &#61; 1797.2 cm&#8722;1. The maximum selectivities measured for oxygen and carbon were <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03B1;</mml:mi></mml:math>(16/18) &#61; 20 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03B1;</mml:mi></mml:math>(12/13) &#61; 25 respectively.

I. K. Bildinov

V. B. Laptev

E. A. Ryabov

L. M. Tumanova

Selective Dissociation of C4F9 COI Molecules by the Second-Harmonic Radiation of Pulsed TEA CO2 Laser

The experimental data on multiphoton excitation of polyatomic molecules in strong fields of high pressure continuously tunable CO2 lasers are presented. The program package for computer simulation of multiphoton excitation spectra and excitation dynamics is developed. Good agreement between computer simulation and experimental data is observed.

B. G. Sartakov

The Spectral Features of Polyatomic Molecules Multiphoton Excitation in a Strong IR-Laser Field