Laboratory of Laser Photochemistry
Institute of Chemical Kinetics and Combustion
The lab’s particular interest lies in the field of gas-phase reactions initiated under IR and UV laser radiation:
1. thermal reactions under continuous wave CO2-laser irradiation,
in homogenious (without affecting of walls) condition and study of such
reaction kinetics;
2. IR multiphoton dissociation of molecules under pulse CO2-laser
irradiation, investigation of reactivity of vibrationally excited molecules
and radicals, development of isotope separation methods;
3. the study of the dissociation kinetics of the molecules excited by pumping
of their vibrational overtones;
4. recombination of free radicals studied by the method of intracavity
laser absorption;
5. gas phase relaxation process studied by measurement of IR luminescence.
The attractive project for the near future is photochemistry center organized by Institute of Chemical Kinetics and Combustion (ICK&G) and Institute of Nuclear Physics (INP) on the base of Free Electron Laser (FEL) developed in the INP.
The FEL is planed to be launched in 1999 with the following characteristics: · generation range from 3 to 50 um with smooth tuning; · pulse time is 3x10-11 s; · pulse energy is 10-3 J; · pulse interval is 5x10-8 s; · average power from 1to 10 kW; · Dl/l 10-4. In frames of this project we are planning the following activities: 1. spectroscopy of excited states of molecules; 2. mechanism of IR Multiphoton dissociation; 3. isotope separation by selective IR multiphoton dissociation of molecules; 4. mode-selective dissociation; 5. interaction of excited molecules with atoms and free radicals; 6. reactions of vibrationally excited radicals; 7. function of vibration excitation of molecules in isotope exchange; 8. effect of molecular vibration excitation on the molecule adsorption and chemosorption.
The Center is expected to have international activities. We are open to any suggestion for cooperation.
Latest results. (in collaboration with FEL-laboratory of Duke University ,USA)
The infrared multiphoton dissociation (IRMPD) of molecules and isotope separation by free electron laser (FEL).
The IRMPD phenomenon was discovered about 20 years ago and has been studied in a number of laboratories all over the world. Usually the resonance radiation of the pulsed CO2-laser has been used. The main disadvantage of CO2-laser is a narrow range of tuning. Modern FELs are able to generate tunable IR-radiation that covers all fundamental molecular vibrational frequencies with very short pulses (10-11-10-12 s ). Note , that FEL radiation has a wide spectral width and a relatively low energy of the micropulse. Therefore it was not clear in advance that FEL radiation could be used for IRMPD of complex molecules. We have successfully performed experiments on IRMPD of ethyl chloride molecules (C2H5Cl-->HCl+C2H4) and chlorodifluoromethan (CHF2Cl=HCl+:CF2). FEL-radiation was tuned in the C-H stretching fundamental region at 3.6 um. The composition of products was determined from IR absorption spectra. We have also tuned the FEL in the C-H (3.5 um) and the C=0 stretching fundamental region (5.7 um) to study the IRMPD of formic acid molecules ( HCOOH=H2O+CO ). The vibrational frequencies of the C=0 band stretch of the H12COOH molecule and H13COOH are 1776 cm-1 (5.63 um) and 1736 cm-1 (5.76 um), respectively. The large isotop shift allows us to tune the FEL in resonance with specific molecular vibrations of either H12COOH or H13COOH. The isotopic composition of carbon monoxide ( CO ) produced in the irradiated gas mixture was analyzed with mass spectrometer. The 13C content in the CO product was raised from natural ~1% up to 20% in the experiments with natural formic acid (~1 Torr) . The obtained results have shown that the use of FELs is applicable for research in traditional areas of IR laser photochemistry and for solution of new scientific and practical problems.
Publications:
1. Abstracts of FEL-users workshop, 1996, Roma.
2. Abstracts of 4th symposium on Laser Spectroscopy,1996,Taejon,Korea.
3. Doklady of Russian Academy of Science,1997,v.352,N6,p. 774-776.
4. J. Korean Phys. Soc., 1997, v.30, N2, p.346-366.
5. "Free electron laser and its application in Asia", 1997, p.245-252,
Tokyo.
6. J.Phys. Chem., 1997, v.A 101, p.7200-7207.
Prof. A. K. Petrov
Institute of Chemical Kinetics and Combustion ul. Institutskaya, 3
630090, Novosibirsk Russia
Phones: (7-383-2)-354150, (7-382-2)-354174
Fax: (7-383-2)-352350
E-mail: petrov@kinetics.nsk.su
INTERNET: http://www.kinetics.nsc.ru/llpc/petrov/petrov.html