Ab initia study of the hyperfine structure of the X ² π electronic state of HCCS

Abstract

The results of an ab initio study of the magnetic hyperfine structure of the X 2 π electronic state of HCCS and DCCS are reported. The potential surfaces for two components of the X 2 π electronic state and the electronically averaged hyperfine coupling constants for H, D, 13 C and 33 S are obtained as functions of two bending vibrational modes by the density functional theory method. Since the bending potential curves calculated in the present study do not differ significantly from their counterparts computed in our previous work by means of an extensive configuration interaction approach, we employ the latter here to avoid the appearance of small differences between the vibronic energy levels presented in this work and those already published. The vibronic wave functions are calculated with the help of a variational approach which takes into account the Renner-Teller effect and spin-orbit coupling. It is found that, due to the generally significant geometry dependence of the hyperfine coupling constants, it is necessary to carry out vibronic averaging of the corresponding functions in order to obtain values which can be compared with the results of measurements. The results of the present study are an aid to the reliable interpretation of recently published experimental data.