Decay Behaviors of H_2~- Anions in Solid Parahydrogen: Effect of Nuclear Spins on Chemical Reactions

摘要

Decay processes of H_2~- anions in γ-rays-irradiated solid parahydrogen were studied by using ESR spectrometer. The following interesting results were obtained. First, the initial amount of ortho-H_2~- anions in the γ-irradiated solid parahydrogen was three times as large as those of para-H_2~1 anions. Second, the amount of para-H_2~- anions decreases faster than that of ortho-H_2~- anions upon storage of the irradiated samples at 4.2 K. Third, the decay rate of H_2~- anions is accelerated by the addition of D_2 molecules. Forth, H_2~- anions at 2.2 K decay faster than at 4.2 K. According to the parity conservation rule in a homonuclear diatomic molecule, the energy of ortho-H_2~- anions at the ground state is lower than that of para-H_2~- anions, whereas that of ortho-H_2 molecules is higher than that of para-H_2 molecules at low temperatures. The first and second results are ascribed to para→ortho conversion of -H_2~- anions. The third result indicates a transformation of -H_2~- anion into H_2+ e~- or H + H~- caused by a distortion of the crystal around D_2 or HD molecules. The forth result suggests a coherent tunneling mechanism of diffusions of H_2~- anions in the solid parahydrogen.