Improved experimental and theoretical energy levels of neon I

The spectrum of neutral neon used as a carrier gas has been measured by the Fourier transform spectroscopy technique from 1800 to 9000 cm −1 . We report on transitions leading to improved energy levels for the 4 f , 5 f , 6 f , 7 f and the 5 g configurations. In addition, we identify transitions leading to the previously unknown 6 g and 7 g configurations. Theoretically, we have generalized the polarization and pair coupling formulae to the extended quadrupole-polarization model. Explicitly accounting for the 6 f' -7 f (6 g' -7 g ) quadrupole interaction, our two-parameter expression reproduces 18 observed levels ( ng ) with a mean deviation of 0.016 cm −1 . Inclusion of the 24 observed pairs of nf levels increases the mean deviation to 0.036 cm −1 .