The crystal spectra of very weak transitions

摘要: The weak absorption system of crystalline naphthalene at 3200 a has been measured 4°K in polarized light. Previous work 20°K is supplemented by number newly recorded lines, and re-measurement the frequencies all lines lower temperature. spectrum compared with vapour corresponding bands identified so far as possible. Exciton resonance effects are analysed discussed. analysis discloses that important b 3 g vibrations upper state 438 911 cm-1 both reduced 5 per cent crystal, smaller changes other vibrations. Comparison shows vibrationally induced bands, even when relatively strong, little influenced intermolecular forces, whereas very pure electronic give evidence much greater effects.