Diode laser probing of the highhyphen;frequency vibrational modes of baths of CO2, N2O, and CO excited by relaxation of highly excited NO2

摘要

Quenching of highly excited vibrational states of NO2in baths of CO2, N2O, and CO has been investigated. Dilute NO2mixtures were excited by a pulse from an excimer pumped dye laser operating at 495 nm. The ngr;3antisymmetric stretching modes of CO2(2349 cmminus;1) and N2O (2223 cmminus;1) and thev=1 level of CO (2143 cmminus;1) were probed with continuous wave IR diode lasers. The amount of energy transferred from excited NO2to the ngr;3modes of both CO2and N2O was found to be 3percnt;plusmn;1percnt; of the original excitation energy. On the other hand, a smaller amount of energy (0.9percnt;plusmn;0.3percnt;) was deposited into the CO vibrational mode for NO2contained in a dilute CO bath. These results support a picture of very inefficient transfer from high energy states of donor molecules to the highhyphen;frequency vibrational modes of small bath molecules. Differences in the efficiency of energy reception by the highhyphen;frequency modes of these three molecules scale roughly as the infrared transition moments for the bath states indicating the importance of resonance effects in the energy transfer process, but a combination of shorthyphen; and longhyphen;range force mechanisms is probably necessary to account for the observed differences.