Lowest Singlet State of p-Chloroaniline in Pure and Mixed Crystals

The lowest 1B2 state of p-chloroaniline has been examined in neat and mixed crystals at 4.2°K. The coupling of the p-chloroaniline electronic state to host phonon modes varies greatly depending on the host. Weak coupling has been observed for a durene host, and stronger coupling with the excitation of pseudolocal phonon modes has been observed with a biphenyl host. The change in dipole moment on excitation to the 1B2 state was +1.26 D. In the neat-crystal spectra large vibronic effects, not present in the mixed-crystal spectra, have been found. These effects, along with a strong depolarization of the vibrational bands in the spectra, indicate a possible vibronic interaction among the factor group states.