Observation of hydrogen localization induced by proton-beam stress in TlH₂PO₄

We have studied the microscopic structure of a proton-irradiated TlH₂PO₄ (TDP) sample under several temperature. The polycrystalline TDP sample was irradiated by a 1-MeV proton beam at a dose of 10¹⁵/cm². In general, solid materials exhibit a proton strong dipolar interaction and anisotropic chemical shifts that cause spectral line broadening and thereby hinder the observation of the crystal structure. Therefore, in order to determine the hydrogen displacements in the hydrogen bonds, one must eliminate dipolar interactions and anisotropic chemical shifts by using a high-resolution technique. Our ¹H combined rotation and multiple-pulse spectroscopy (CRAMPS) nuclear magnetic resonance (NMR) measurements indicate that the proton-irradiation stress causes a local strain change, implying the existence of a proton displacive component remaining on the structural modification of the O-H.O bonds.