ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The quantum yields of sensitized biacetyl phosphorescence emission have been determined for SO2-biacetyl-CO2, SO2-biacetyl-N2, and SO2-biacetyl-CO mixtures irradiated at 2875 Å. Series of experiments were made at various SO2, biacetyl, and added-gas concentrations (up to 4 × 10-2 M). The kinetic data show an “excess” biacetyl emission which requires the participation of some undefined excited state or isomer of SO2 in addition to the emitting singlet (1SO2) and triplet (3SO2) states of SO2. These results confirm the experimental observations of Cehelnik et al. [12] and Wampler et al. [9] who reported that an “excess” quantum yield of CO2 occurred in 3130 Å-irradiated SO2-CO mixtures at high CO pressures. The kinetic analysis of the data is most consistent with the hypothesis of Wampler et al.; the nonreactive, undefined excited state or high-energy isomer of SO2, designated here as X, is formed in part as 1SO2 is quenched: 1SO2 + M → (SO2—M) (1); 1SO2 + M → 3SO2 + M (2); 1SO2 + M → X + M (3). X itself does not transfer energy to biacetyl. It decays largely by a nonradiative first-order process at low pressures, X → SO2 (5), but it generates 3SO2 by collisional perturbation at high pressures, X + M → 1SO2 + M (4). In terms of this mechanism, the following rate constant ratios are derived from the present study: k2/(k1 + k2 + k3) = 0.020 ± 0.010 (M = CO2), 0.021 ± 0.010 (N2), 0.019 ± 0.010 (CO); k3/(k1 + k2 + k3) = 0.14 ± 0.02 (M = CO2), 0.085 ± 0.012 (CO), 0.11 ± 0.02 (N2); and k5/k4 (mole/l) = 0.020 ± 0.004 (M = CO2), 0.016 ± 0.003 (CO), 0.021 ± 0.005 (N2).
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550050207
