It was difficult to identify any vibrational progressions in the near-uv spectra, but the three highest energy bands of Fig. , centered at 28637, 28788, and 28938 cm -1 , were consistent with a bending progression with an upper state vibrational frequency near 150 cm - 1 . The band at 28637 cm -1 was the most intense feature in this spectral range. If it is assumed to be an electronic origin band, the calculations indicate that the upper state is 6 2 A' (cf. Table ).