Multiple quantum NMR dynamics in a gas of spin-carrying molecules in fluctuating nanopores

The effect of Gaussian fluctuations of nanopores filled with a gas of spin-carrying molecules ($s=1/2$) on the multiple quantum (MQ) NMR dynamics is investigated at different variances and correlation times of the fluctuations. We show that the fluctuations smooth out the evolution of MQ NMR coherence intensities which rapidly oscillate as functions of time in the absence of fluctuations. The growth and decay of the MQ coherence clusters in the fluctuating nanopore are also investigated.Comment: 10 pages, 3 figure

NMR line shapes of a gas of nuclear spin-1/2 molecules in fluctuating nano-containers

Reported in this paper is the impact of the fluctuations of the geometry of the nano-meter gas containers in the medium on the NMR line shape of the gas inside of the nano-containers. We calculate exactly the NMR line shape of the gas of spin-1/2 carrying molecules for two typical dynamics of the nano-container volume and the orientation with respect to the external magnetic field: (i) for a Gaussian stochastic dynamics, and (ii) for the regular harmonic vibrations. For the Gaussian ensemble of static disordered containers having an infinite correlation time, $\tau_{\sf c} \to \infty$, the overall line shape is shown to obey a logarithmic low frequency asymptotics, $I(\omega) = {const} \times \ln (\frac{1}{\omega})$, at $\omega \to 0$, and exponentially decaying asymptotics in a high frequency domain. For the Gaussian ensemble of the rapidly fluctuating containers of a finite $\tau_{\sf c}$, the overall line shape has a bell-shaped profile with $\sim \omega^{-4}$ far wing behaviour. In addition, we calculate exactly a satellite structure of the NMR line shape when the nano-bubbles in a liquid are affected by the harmonic deformations due to the acoustic waves.Comment: 14 pages, 4 figure