Experimental determination of the mechanism of the tunneling diffusion of H atoms in solid hydrogen; Physical exchange versus chemical reaction

Kumada, Takayuki   

Effect of pressure on the recombination of H atoms produced by UV-photolysis of O-doped solid H was studied using ESR spectroscopy. The recombination rate constant was independent of pressure up to 13 MPa below 4.2 K, whereas it remarkably decreases with the increase in pressure above. The absence of pressure effect indicates that the H atoms do not diffuse by the physical exchange of positions with neighboring H molecules, but by the tunneling reaction H + H H + H.