ROTATION OF CN IN SOLID RARE-GASES

The band shapes of the infrared fluorescence from the nu = 1-4 X 2SIGM A levels of CN isolated in rare gas matrices are investigated using a high-resolution Fourier-transform spectrometer. The spectra suggest ne arly free rotation in solid Xe, with barriers to rotation increasing f or the lighter rare gases. The rates of nonradiative A 2PI <-- --> X 2 SIGMA relaxation processes decrease sharply in the same direction. Sim ulation of the rovibrational lineshape assuming a free rotator shows s atisfactory 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 th e relaxation of matrix-isolated CN.