Sm. Ball et G. Hancock, THE RELATIVE QUANTUM YIELDS OF O-2(A(1)DELTA(G)) FROM THE PHOTOLYSIS OF OZONE AT 227K, Geophysical research letters, 22(10), 1995, pp. 1213-1216
The relative quantum yields of O-2(a(1) Delta(g)) from the photolysis
of ozone have been measured at 227(+/-2)K over the wavelength range 30
0nm greater than or equal to lambda greater than or equal to 322nm, an
d are compared to those measured previously at 298K [Ball et al., 1993
]. The yields at the two temperatures show the same initial wavelength
dependence in the fall-off region, in contrast to literature measurem
ents of the O)(D-1) yields which show a shift;in the fall-off curve to
shorter wavelengths at low temperature. For lambda > 309nm, the yield
at 227K falls more rapidly than that at 298K, confirming that interna
l energy mediated dissociation of ozone provides the major source of O
-2(a(1) Delta(g)) at wavelengths just beyond the 310nm threshold for t
he spin allowed production, of the two singlet products. However, the
yields of O-2(a(1) Delta(g)) at 227K and 298K were found to be approxi
mately equal for photolysis wavelengths lambda greater than or equal t
o 320nm, and substantially larger than O(D-1) yields predicted from mo
delling currently available for the photolysis of vibrationally excite
d ozone. These results suggest the existence of a spin forbidden disso
ciation channel for O-2(a(1) Delta(g)) with a quantum yield of Phi = 0
.1 at wavelengths near to 320nm.