ELECTRONIC AND VIBRONIC DIPOLE-MOMENTS OF CH2D+

Isotopic substitution of a hydrogen atom by deuterium turns a non-pola r ion such as CH3+ into a non-centrosymmetric system, CH2D+, suitable for rotational spectra detection in space. The vibrational contributio n to the dipole moment of the ion is investigated in this paper. The e lectronic potential surface has been obtained in a first-order CI, sta rting from a full valence active space built by using projected locali zed orbitals, to which core valence correlation effects have been adde d to account for rehybridization. The vibrational functions are obtain ed in a basis of harmonic oscillators. Three levels of vibrational tre atment are presented, i.e, harmonic, non-coupled and coupled modes. Th e final result for the transition moment in the lowest vibrational lev el, mu(v) = 0.327 Debye, shows that CH2D+ should be observed and may b e a useful tracer of CH3+ in interstellar chemistry.