ABINITIO CI CALCULATION OF NUCLEAR-QUADRUPOLE COUPLING-CONSTANTS OF LOW-LYING ROVIBRATIONAL LEVELS IN THE X 1-SIGMA+ STATE OF CH+

The H-2 and C-11 quadrupole coupling constants of rovibrational levels of (CH+)-C-12-H-2, (CH+)-C-11-H-1 and (CH+)-C-11-H-2 in their ground electronic state have been calculated from molecular wavefunctions which explicitly describe nuclear displacement. The deuteron coupling is found to be weak, its strength decreases with vibrational excitation. The ''C coupling is predicted to be relatively very strong for both the isotopic variants. The vibrational dependence of the C-11 coupling is found to be rather insignificant. The quadrupole hyperfine patterns of (CH+)-C-11-H-2 are predicted to be dominated by the relatively very strong C coupling and their basic features are found to be independent of the vibrational state considered. The rotational dependence of both the H-2 and C-11 coupling constants is seen to be quite unimportant. The main features of the deuteron quadrupole coupling in CH+ are analogous to those of the isoelectronic BH.