Interactions between molecular hydrogen and alkali halide ion-pairs in neon matrices

Neon matrices of the alkali halide ion-pairs and H-2 give evidence of associations as characterized by infrared absorptions in, the H-H stretching region. With the exception of KF, none of the absorptions correlated with analogous species in argon matrices. It was exceedingly difficult to obtain the 1:1 complex of MX:H-2 because of the extreme mobility of H-2 in the developing matrix, and concentrations of less than 70 ppm were necessary to achieve adequate dilution. Lil, LiCl, and CsF all induce infrared intensity in H-2 that is at higher wavenumber than what is seen in argon, and it is argued that the differences are due to an interaction which is fundamentally different from what is seen in argon. While it has been argued that dihydrogen interacts exclusively with the anion of alkali halides in argon, it is clear from these spectra that there must be at least some cation interaction as well.