Inelastic squared form factors of the vibronic states of B1Σu+, C1Πu, and EF1Σg+ for molecular hydrogen deuteride studied by fast electron scattering

A joint experimental and theoretical investigation of the valence-shell excitations of hydrogen deuteride has been performed by the fast electron impact method at an incident electron energy of 1500 eV and the multireference single- and double-excitation configuration-interaction method. Momentum-transfer-dependent inelastic squared form factors for the vibronic states belonging to the B-1 Sigma(+)(u), C-1 Pi(u), and EF1 Sigma(+)(g) of molecular hydrogen deuteride have been derived with a high-energy resolution of 70 meV. Similar to the results of molecular hydrogen [L. Q. Xu, K. Xu, Y. G. Peng, X. Xu, Y. W. Liu, Y. Wu, K. Yang, N. Hiraoka, K. D. Tsuei, J. G. Wang, and L. F. Zhu, Phys. Rev. A 97, 032503 (2018)1, the present calculations do not satisfactorily reproduce the profiles of the inelastic squared form factors for the higher vibronic states of the B-1 Sigma(+)(u) of hydrogen deuteride. However, the discrepancies between the experimental and calculated results of the B-1 Sigma(+)(u) of hydrogen deuteride show a weaker dependence on the vibronic number than those of molecular hydrogen, i.e., the present experimental results for the B-1 Sigma(+)(u)of hydrogen deuteride are in better agreement with the calculated ones than those of the molecular hydrogen. It is very likely that the electronic-vibrational coupling effect in hydrogen deuteride is less important than that in molecular hydrogen. For the C-1 Pi(u) state and some vibronic excitations of the EF1 Sigma(+)(g) state, the present experimental results are lower than the present calculations, which may be due to the fact that the first Born approximation does not hold at an incident electron energy of 1500 eV.