ROTATION OF CN IN SOLID RARE-GASES

The band shapes of the infrared fluorescence from the nu = 1-4 X 2SIGMA levels of CN isolated in rare gas matrices are investigated using a high-resolution Fourier-transform spectrometer. The spectra suggest nearly free rotation in solid Xe, with barriers to rotation increasing for the lighter rare gases. The rates of nonradiative A 2PI <-- --> X 2SIGMA relaxation processes decrease sharply in the same direction. Simulation of the rovibrational lineshape assuming a free rotator shows satisfactory agreement with the observed spectra in xenon and krypton. This provides confirmation for earlier studies, both experimental and theoretical, suggesting that rotation may play an important role in the relaxation of matrix-isolated CN.