Energy-dependent energy transfer: Deactivation of azulene (S, Evib) by 17 collider gases

Abstract

Collisional deactivation of highly vibrationally excited azulene in the electronic ground state was investigated using infrared fluorescence detection. Azulene (S0, E) was prepared with E≂17 500 cm−1 and E≂30 600 cm−1 by laser excitation at 600 and 337 nm, respectively. Advantage was taken of the fast internal conversion rate to S0 azulene from S1(600 nm) and S2(337 nm) electronic states. The collider gases investigated are He, Ne, Ar, Kr, Xe, H2, D2, N2, CO, O2, CO2, H2O, NH3, CH4, SF6, n-C4H10, and unexcited azulene. The results are expressed in terms of 〈ΔE(E)〉, the average energy transferred per collision, which can depend on the vibrational excitation energy E of the azulene. Using previously obtained knowledge of the dependence of infrared fluorescence intensity on E [M. J. Rossi and J. R. Barker, Chem. Phys. Lett. 85, 21 (1982)], two methods were used to obtain 〈ΔE(E)〉 values from the fluorescence decay curves: (1) an approximate method that considered only the average energy, and (2) solution of the full collisional master equation. Both methods gave 〈ΔE(E)〉 values that depend strongly on E. The limited experimental information on the identity of the energy-transfer processes operative in the deactivation of azulene is discussed. Additional experimental results on vibration-to-vibration energy transfer from azulene to CO2 are presented, which indicate that the emission at 4.3 μm observed previously [J. R. Barker, M. J. Rossi, and J. R. Pladziewicz, Chem. Phys. Lett. 90, 99 (1982)] originates not only from CO2(001), but from other states with one quantum of excitation in ν3. The experimental results are discussed in terms of models for energy transfer, which have appeared in the literature. It is concluded that only a superficial understanding exists and theory has lagged far behind experiments on energy transfer.

Collisional energy transfer probabilities of highly excited molecules from kinetically controlled selective ionization (KCSI). II. The collisional relaxation of toluene: P(E′,E) and moments of energy transfer for energies up to 50 000 cm−1

“…So far, the larger fraction of the many direct experiments on CET of highly vibrationally excited polyatomic molecules have dealt with monitoring the energy loss of excited donor molecules, among others, e.g., of toluene-d 0 and -d 8 , 4͑b͒-8 azulene-h 8 and -d 8 , [9][10][11][12][13][14][15] benzene-h 6 and -d 6 , 4͑b͒, 16,17 hexafluorobenzene ͑HFB͒, 18,19 and pyrazine. [20][21][22][23][24] Others have monitored the uptake of energy in the bath medium during the relaxation by various techniques [25][26][27][28][29][30][31][32][33][34] or even identified state-specifically the energy transferred, e.g., to CO 2 colliders in single collisions.…”

Photodissociation dynamics of azulene

“…These molecules are frequently used in the study of energy transfer. [13][14][15][16][17][18][19][20] In contrast to the S 1 and S 2 states, the photophysical properties of the higher electronic states have received little attention. The excitation into higher states, like S 3 and S 4 , shows almost the identical fluorescence spectra from molecules in the S 2 state.…”

Collisional quenching and depolarization of the fluorescence of the 2,5-diphenyloxazole and 2-phenylbenzoxazole vapors by oxygen

“…This relation is particularly convenient if the gas-kinetic collision characteristics of quenching and unquenching gases are identical or nearly the same. As such gases, one can use oxygen and nitrogen that does not quench excited electronic states; the molecules of these gases are very close in their gaskinetic collision characteristics [9,10]. If the assumption that k z,M [M]s M .…”