Strong Collision Induced Spin-Lattice Relaxation for Tunneling NH4-ion Systems in the Rotating Frame

Abstract

Abstract In order to calculate the rotating frame spin-lattice relaxation time T1ρ for tunneling NH4-ion systems at low temperature, a model of relaxation, which is available when γHL τr⪢1, is proposed, where HL is the local dipolar field and τr the correlation time. The present model is useful especially in two cases: (1) when the NH4-ion is relatively magnetically isolated and the assumption of a common spin temperature cannot be used. (2) when the level crossing of the NH4-ion occurs in the rotating frame. In case (1), non-single exponential relaxation is predicted. In case (2), T1ρ is shown to be proportional to τr, while the prediction of the weak collision theory is T1ρ ∞cc τr-1. The present model is compared with the strong collision theory of Slichter and Ailion.