The vibrational spectrum and structure of ((2)Sigma(+))He-MgH2+ 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 ma(0) from those corresponding to the ab initio potential surface minimum. Vibration transition moment integrals and associated radiative properties of ((2)Sigma(+))He-MgH2+ have been calculated using an adapted quadrature scheme, in conjunction with an embedded analytical UCCSD(T) dipole moment function. (C) 2008 Elsevier B.V. All rights reserved.