Diode laser probing of the low frequency vibrational modes of baths of CO2 and N2O excited by relaxation of highly excited NO2

Quenching of highly excited vibrational states of NO2 in baths of CO2 and N2O has been investigated. Dilute NO2 mixtures were excited by a pulse from an excimer pumped dye laser operating at 495 nm. Various vibrational modes of the bath gases were probed with continuous wave IR diode lasers. Less than 20% of the energy initially placed in the NO2 by the dye laser is taken up by the vibrational degrees of freedom of the CO2 or N2O baths. For N2O, the three different vibrational modes (ν1=1285 cm−1, ν2=589 cm−1, ν3=2223 cm−1) take up almost equal amounts of energy from NO2, but the number of vibrational quanta produced in the bath is found to increase with decreasing vibrational frequency. Similar results are found for CO2 except that the ν1 and ν2 modes cannot be studied separately for this bath gas due to rapid ν1↔ν2 intermode equilibration.