Low temperature properties of proton and deuteron glasses

Abstract

2D deuteron exchange NMR and 87 Rb spin-lattice relaxation time measurements in proton and deuteron glasses show that the O-H..O dipoles are not completely frozen out at low temperatures but show dynamic features characteristic of incoherent tunneling. RADP and DRADP are thus quantum glasses.

Quantum tunnelling in the hydrogen bond

“…In Fig. 24 the inverse temperature dependence of the two relaxation times are plotted for RADP (x = 0.5) and DRADP (x = 0.42) [75][76][77]. All curves exhibit a similar qualitative shape with a T 1 minimum developing into a low temperature plateau with decreasing temperature.…”

“…The hydrogen bond motion in proton glasses is also revealed in 2 H NMR lineshape investigations of the deuterated materials [76,78]. Here the transitions arising from the deuterons in the individual hydrogen bonds are resolved and deuteron exchange gives rise to the classic chemical exchange behaviour in the spectrum.…”

1H–19F spin–lattice relaxation spectroscopy: Proton tunnelling in the hydrogen bond studied by field-cycling NMR

“…(7) is negligible (s À1 exc ¼ 0), s À1 c ð1=TÞ has been modelled to provide R 1 ð1=TÞ and R 2 ð1=TÞ from Eqs. (2), (3), (4), and (6). The values of the Arrhenius rate parameters were chosen to be equal to the values determined for benzoic acid (s À1 0 ¼ 5 Â 10 11 s À1 , DE act ¼ 600K [7,11,26]) and the modelled behaviour is shown with solid lines in Fig.…”

“…For fundamental investigations of the proton transfer process, solid-state NMR is well-suited to characterising the hydrogen dynamics [3][4][5][6][7]. The role of tunnelling can be a complex one so it is important to investigate model systems to gain fundamental insight into the proton transfer process as well as to provide a platform for a deeper exploration of the experimental protocols used to investigate the dynamics.…”

Study of nuclear quadrupole interactions and quadrupole Raman processes of 69Ga and 71Ga in a β-Ga2O3:Cr3+ single crystal

“…The temperature dependence of the relaxation time is indicative of fluctuations in the EFG tensor driven by thermally activated motion. For I = 3/2, relaxation transition probabilities can be described by [20,23,24]:…”