Ab initio structures and stabilities of helide cations: HeXn+ (X = B-Ne, Al-Ar and n = 1-3)

The electronic structure and molecular properties of helides of the form He Xn+ (where X = B-Ne, AI-Ar and n = 1-3) were studied using the CCSD(T) meth od in conjunction with the series of correlation-consistent basis sets. The highest level of theory employed, the CCSD(T)-FC/cc-pVQZ model, was used t o elucidate trends in bond lengths, dissociation energies and harmonic freq uencies. The more highly charged species were found to have shorter bond le ngths than the singly charged species. The ground states of the helide cati ons were often those with longer bond lengths when compared with the excite d state ions.