The pressure effect on the recombination and relaxation of hydrogen atoms in solid hydrogen

We have studied experimentally for the first time the properties of hydrogen atoms in solid hydrogen under pressure. The recombination rate constant has activation-type temperature dependence in the pressure range from 0 to 22 MPa. The activation energy increases linearly with external pressure Ea=(2.4 P+106 K), as should be expected in the case of a tunneling vacancy mechanism in atom diffusion. Strong pressure effects on the linewidth of the ESR signal and on the spin–lattice relaxation time T1 were explained by the competition between the local ortho–para conversion process around the H atom and the pressure-dependent diffusion.