Trapping mechanism and sites of H and D atoms in solid Ne

The shifts of the isotropic Fermi contact hyperfine interactions (FCHFI) of hydrogen or deuterium atoms isolated in crystalline noble gases at cryogenic temperatures are compared to the values of the same quantities of the hydrogen atom in the gas phase. New experimental FCHFI values of H/D trapped in crystalline Ne are compared with experimentally obtained and theoretically computed values. The possible trapping sites in the distorted solid Ne gas crystalline structure occupied by the hydrogen atomic impurities are identified by the variation of the FCHFI shifts in the EPR spectra and discussed after their dependence to the deposition method. The present EPR investigation revealed formation of H-2 microcrystals in solid Ne even at a very low H-2 impurity content of 0.01% in the deposited H-2:Ne gaseous mixture.