On the existence of H- in γ-irradiated matrices at 77 K

A band peaking around 1050 nm in the stimulated neutralization luminescence spectrum of γ-irradiated glassy EtOH, pure crystalline and alkaline glassy ices has recently been attributed to H-. Further results on EtOH glass and on EtOH-H2O mixtures are now presented which support our previous interpretation. A shuttle of the electron from the presumed H- to a matrix trapped state and back to H with restoration of the 1050 nm band can be induced in, and only in, alcohol-water mixtures where it has been shown that, contrary to either of the two pure solvents, H atoms can be trapped (Hsub(t)). Further, the intensity of the regenerated stimulated band is found to be maximum for the mixture composition which leads to the highest Hsub(t) yield. It is noted that the red limit of the H- stimulated band, which corresponds to a photodetachment energy threshold, is close to the electron affinity value of the isolated H atom. This observation seems to imply that, contrary to expectation, the solvation energy of H- in these matrices is quite low. (author)