A method is proposed whereby vibrational frequency shifts can be calculated in weakly bound heteroclusters and is applied to the ionic N2+-Hen clusters. We use diffusion Monte Carlo to simulate the 3n degrees of freedom of the N2+-Hen interactions while the N-N vibrational motion is solved by an adiabatic method. In addition, we report minimum energy structures, vibrationally averaged structures and binding energies for N2+-Hen clusters for n = 1-12.
