Quantum tunneling of D(H) atoms and H-2 anions in solid hydrogen

This paper contains three results. First, the rate constants for the tunneling reaction HD + D --> H + D-2 in solid HD increase steeply with increasing temperature above 5 K, while they are almost independent of temperature below 5 IC. A mechanism of a vacancy-assisted tunneling reaction is proposed to account for this temperature dependence. Second, a hydrogen atom and a hydrogen molecule form a van der Waals complex in the Ar matrix at 20 K, where the tunneling reaction HD + D --> H + D-2 takes place in this complex. The analysis of well-resolved ESR spectra of the complex determined the distance between a hydrogen atom and a hydrogen molecule as 2.3-2.5 Angstrom. Third the decay rate constants of H-2(-) anions in solid parahydrogen decrease with decreasing temperature below 6.6 K, attain the minimum value at 5 Ii; and then increase with decreasing temperature in the range of 5 --> 2.7 K. The abnormal temperature dependence of the decay rate constants below 5 K is ascribed to a phonon-scattering process of quantum diffusion.