TheD²Σ⁺-X²Σ⁺Band System of CaH

Abstract

The D2Σ+-X2Σ+ band system of CaH has been reinvestigated in emission and in absorption. Analysis shows that the previously accepted vibrational numbering must be changed with the result that the vibration frequency of the D state must be reduced by a factor of two. Anomalies in the rotational structure of the D state are explained by a strong homogeneous interaction with excited vibrational levels of B2Σ+.

Ab initio calculation of rovibronic transition spectra of CaH

“…This point was revisited in more recent works. 4,5 Mulliken and Christy 6 tried to find an explanation from a quantum chemical point of view, but did not succeed. It was only after the publication of the quantum chemical calculations of Honjou et al 7 and Jeung et al 8 that multiple crossings between the ionic and neutral configurations were clearly shown to create very irregular potential energy ͑PE͒ curves.…”

Fourier transform emission spectroscopy of the E2Π–X2Σ+ transition of CaH and CaD

“…The anomalies in the rotational structure of the D 2 R + state were explained by strong homogeneous interaction with the higher vibrational levels of the B 2 R + state. A comparison of our E 2 P state term values for CaH to those of the D 2 R + vibrational levels [36] indicates that the D 2 R + state is not responsible for perturbations in the v = 1 vibrational level of the E 2 P state. As suggested previously, the perturbations observed in the v = 1 level of the E 2 P state are most probably caused by the higher vibrational levels of the B 2 R + state.…”

“…In a study of CaH, Bell et al [36] obtained a rotational analysis of the D 2 R + -X 2 R + transition and revised its vibrational assignment. This analysis reduced the vibrational frequency of the D 2 R + state by a factor of two.…”

Fourier transform emission spectra of the A2Π→X2Σ+ and B2Σ+→X2Σ+ transitions of CaD

“…Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/ 10.1016/j.jms.2012.10.001. À5.88 (17) a The numbers in parentheses are 1r uncertainties in the last quoted digits. Table 5 Equilibrium constants (in cm À1 ) for the X 2 R + , A 2 P and B 2 R + states of CaD.…”

“…Parallel to the early studies on CaH, the B 2 R + -X 2 R + spectrum of CaD was photographed by Watson in 1935, and the 0-0 and 1-1 bands were rotationally analyzed [8]. Electronic transitions of CaH involving the X 2 R + ground state and several low-lying excited states, i.e., A 2 P, B 2 R + , C 2 R + , D 2 R + and E 2 P states were studied in the 1970s [9][10][11][12][13][14][15][16][17][18], while only the D 2 R + -X 2 R + spectrum was recorded for CaD [19]. Martin used spectroscopic data from both CaH and CaD to generate a set of empirical potential energy curves for the three lowest 2 R + states of CaH [20].…”