Reorientational and angular momentum correlation times in gaseous tetrafluoromethane at moderate densities

Abstract

NMR 19F spin-lattice relaxation times and Raman 435 cm-I doubly degenerate [v,(e)] vibrational-rotation band shapes have been measured in gaseous carbon tetrafluoride at 25·C and densities of 9 to 120 amagat. NMR spin-lattice relaxation times have also been measured over the temperature range of -60 to 4O·C for the above densities. The Fourier transform analysis of the Raman band shapes has allowed us to calculate the reorientational correlation time T6>" Since spin rotation interactions provide the dominant relaxation mechanism for fluorine in CF 4 , then the angular momentum correlation time T J is obtained directly from the 19p T I relaxation times with the assumption that the anisotropy of the spin-rotation interaction tensor is small. A comparison of our experimental T e.' and T J relationship agrees well with that predicted by the dilute gas limit of Gordon's Jand M -diffusion model as extended to classical spherical molecules by McClung.

Molecular reorientation of CD4in gas‐phase mixtures

“…Also shown are the results from 19 F relaxation experiments on CF 4 . 63 For CF 4 , the extended diffusion model agrees very well with experiment.…”

Spin–spin coupling in the HD molecule determined from 1H and 2H NMR experiments in the gas-phase

“…Particularly, for the dipolar, quadrupolar, and spin-rotation relaxation the relevant interaction strengths are determined by the gyromagnetic ratios of the proton and the deuteron, the quadrupole moment of the deuteron, and spin-rotation constants of the HD molecule, respectively. When considering the gas phase, the correlation time for changes of the angular momentum vector and the correlation time for molecular reorientation are positively correlated [26], and at sufficiently high pressure the relaxation time is directly proportional to the gas density [27][28][29]. Indeed, a series of experiments conducted by Beckmann et al [30] confirmed that the minimum T 1 dependence on pressure is approximately 0.5 bar for molecular hydrogen.…”