It has been shown that out of plane hydrogen wagging vibrations of CH groups, adjacent to the heteroatoms, are responsible for the appearance of relatively strong, in plane polarized bands in π*âπ phosphorescence of p methoxybenzaldehyde and dibenzo[f, h]quinoxaline. In dibenzo[f, h]quinoxaline, these hydrogen vibrations are more effective than the out of plane ring vibrations in inducing the in plane polarized phosphorescence intensity through vibronic spin orbit coupling. In dibenzo[a, c]phenazine, where there is no CH group adjacent to the nitrogen atoms, the vibrational modes which give rise to the more intense in plane polarized bands are out of plane ring modes. These results indicate that the nπ* state(s) is involved as an intermediate state(s) in vibronic spin orbit coupling. © 1969, American Institute of Physics. All rights reserved.
