Spectroscopic identification of the lowest rotation–vibration levels of the (2pσ)2 F 1Σ+g state of the D2 molecule

Abstract

The previously unobserved lowest vibrational levels of the F state of D2 are detected by the identification of F 1Σ+g–B 1Σ+u bands in infrared emission spectra of electric discharges recorded with a Fourier–transform spectrometer. The rotation–vibration structure of the F state, v=0–5, J=0–5, is in good agreement with accurate ab initio calculations which include the effects of tunneling in the double-minimum potential of the EF 1Σ+g state. For the v=J=0 levels of H2 and D2 the absolute energy error of the ab initio calculation extrapolates, for infinite nuclear mass, to an error of the electronic F state energy of +0.7±0.1 cm−1. This is consistent with Jungen’s recent accurate spectroscopic determination of the ionization potentials of the excited states of H2.