Mechanism of H2- formation in solid hydrogen

The singlet and the triplet ESR lines with the common g-factor of 2.0023 and the hyperfine coupling constant of 20.3 mT observed after γ-irradiation of crystalline para hydrogen at 4.2 K agreed with the expected ESR spectra of the radical anions of the para and the ortho hydrogen molecules, respectively. A novel model has been proposed for explaining the formation and stabilization of H2- in crystalline H2. The model assumes H2- to be located at the center of a cavity which has previously been occupied by a trapped electron. The excess electron of H2- is forced to be attached on one H2 in the cavity due to strong repulsive interactions between the excess electron and H2 molecules surrounding the cavity. A quantum-mechanical calculation shows that an electron trapped in the vacancy of crystalline H2 automatically converts to H2- by drawing one of the surrounding H2 molecules into the center of the vacancy. (author)