The EF and GK1Σ g+ states of hydrogen : Calculation of nonadiabatic coupling

Abstract

The mutual vibronic coupling between the EF and GK states of hydrogen has been computed in an adiabatic basis of electronic-vibrational states. The electronic matrix elements 〈 EF|▿ R| GK〉 and 〈 EF|Δ R| GK〉 are presented over the relevant range 2.0 ≤ R ≤ 4.0 a.u. and the vibronic coupling matrix is displayed for H 2. Nonadiabatic vibroic energies and B values are calculated for H 2, HD, and D 2 and compared with experimental data. The irregularities of the observed vibronic EF and GK progressions are well reproduced by the calculation. The remaining errors of the calculated energies grow systematically as the dissociation limit is approached, indicating the importance of additional nonadiabatic interactions with higher states and possibly of R-dependent errors of the Born-Oppenheimer energies of the EF and GK states at R values far from the potential minima.