Low Temperature Physics: 29, 792 (2003); https://doi.org/10.1063/1.1614194 (3 pages)
Физика Низких Температур: Том 29, Выпуск 9-10 (Сентябрь 2003), c. 1045-1048    ( к оглавлению , назад )

The contribution of tunnelling to the diffusion of protons and deuterons in rare gas solids

Martin K. Beyer1, Elena V. Savchenko2, and Vladimir E. Bondybey1

1Institut für Physikalische und Theoretische Chemie, Technische Universität München, 4 Lichtenbergstraße, Garching 85747, Germany
E-mail: beyer@ch.tum.de;
bondybey@ch.tum.de

2 B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: savchenko@ilt.kharkov.ua

Аннотация

The stability and diffusion of protons and deuterons in rare gas matrices are reexamined. These are known to be stabilized in rare gas matrices in the form of linear, centrosymmetric Rg2H+ cations. The elementary step in their diffusion, displacement from one Rg–Rg bond to a neighboring one, can be modelled as an isomerization of the triangular Rg3H+ cation. Using an analytic approximation for thermally averaged transmission coefficients for tunnelling through and reflection by a truncated parabolic potential barrier (R.T. Skodje and D.G. Truhlar,J. Phys. Chem. 85, 624 (1981)) we calculate the rate constants for this elementary diffusion step. The calculated rate constants are consistent with all experimental observations, and confirm that tunnelling makes the dominant contribution to the diffusion of protons and deuterons in rare gas solids. Deuteration reduces the tunnelling rates by 5 to 8 orders of magnitude, which agrees with the observation that D+ in rare gas solids is signficantly more stable than H+.

PACS:
47.45.-n - Rarefied gas dynamics
63.50.+x - Vibrational states in disordered systems
66.30.Dn - Theory of diffusion and ionic conduction in solids