Absorption spectra in the vacuum ultraviolet and the ionization potentials of naphthalene and naphthalene-d8 molecules

The vapour absorption spectra of naphthalene and naphthalene-d8 were obtained photographically and photoelectrically from 50000 to 70000 cm-1. A series of Rydberg transitions and possibly two p*-p systems are observed. Each of the five Rydberg series converges to an ionization potential of 65620 ± 40 cm-l, i.e. 8.136 ± 0.005 eV (C10H8), and 65640 ± 60 cm-l, i.e. 8.138 ±0.008 eV (C10D8). The quantum defects of the series are (0.94, 0.88, 0.82, 0.67, 0.53) ± 0.01. The significance of these results is discussed.