ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The kinetics of fluorescence decay of SO2 excited in the 2975-3273 Å region was studied using a powerful, frequency doubled, tunable dye laser system. The existence of two emitting species, first observed by Brus and McDonald, was confirmed. The collision-free lifetimes of the long-lived (L) species ranged from 100 to 300 μsec and the short-lived (S) species from 17 to 43 μsec over the wavelength range employed. The magnitude of the bimolecular quenching rate constant for the L state was a function of the excitation energy; the data show that about 1 kcal/mol of internal energy is lost per collision of the SO2(L) species excited in the range of 2998-3107 Å. Studies of the relative initial fluorescence intensity of the S to that of the L state (IS°/IL°) were made in experiments which extended to 0.11 mtorr. The pressure dependence of the IS°/IL° ratio for experiments at 3107, 3211, and 3225 Åproved that the S and L states do not decay independently. Either efficient bimolecular S → L conversion occurs or bimolecular S ⇄ L interconversion of both states is important. These data coupled with spectroscopic studies of Hamada and Merer and Shaw and coworkers favor the designation of the S and L states as SO2(1A2) and SO2(1B1), respectively. However, if the assignment is correct, then the band origin of the 1B1 state must be at a somewhat longer wavelength, λ〉 3273 Å than tentative spectroscopic assignments suggest. Bimolecular quenching rate constants for the L and S components with various atmospheric gases were determined in 3130- and 2662-Å studies.
Additional Material:
16 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550100202
