Ab initio vibrational spectrum of

The vibrational spectrum and structure of ( 2 Σ + ) He – MgH 2 + has been investigated using relativistically-corrected UCCSD(T). Vibrational wave functions for low-lying l = 0 states were obtained numerically using a w co-ordinate Eckart–Watson vibrational Hamiltonian, in conjunction with an embedded analytical UCCSD(T) potential. For the ground vibrational state, vibration-averaged Mg–H and Mg–He bond lengths differ by −33 and 53 ma0 from those corresponding to the ab initio potential surface minimum. Vibration transition moment integrals and associated radiative properties of ( 2 Σ + ) He – MgH 2 + have been calculated using an adapted quadrature scheme, in conjunction with an embedded analytical UCCSD(T) dipole moment function.