Rydberg transitions in the H2Se molecule

Six of the seven optically allowed series in the vacuum ultraviolet photoabsorption spectrum of H 2 Se have been observed at high resolution (+or-0.003 AA for sharp lines). They are attributed to the excitation of one electron from the outermost molecular orbital to four d- and two p-like orbitals, while transitions to the s-like orbital appear to be absent. The authors have followed one of the series to a principal quantum number n=31, and hence determined an accurate value for the ionisation potential I=79824+or-1 cm -1 . Comparisons are made with the spectra of H 2 O and H 2 S.