ELECTRONIC-SPECTRA OF N2+-(HE)N (N = 1, 2, 3)

Ionic clusters of nitrogen and helium have been investigated by recording their electronic spectra in the near UV. Structured bands belonging to N-14(2+)-He, N-14(2+)-(He)2, N-14(2+)-(He)3, and N-15(2+)-He have been measured between 390 and 392 nm close to the N2+ B 2-SIGMA(u+) <-- X 2-SIGMA(g+) band origin. Spectra were obtained by exciting mass selected cluster cations with tunable laser radiation and recording the photodissociation cross section as a function of wavelength. The data support the hypothesis that the He---N2+ interaction potential has only a small barrier to internal rotation in both the X and B electronic states. A lower estimate for the dissociation energy of the N2+-He cluster of 101 cm-1 is inferred.