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Inert fluorinated gas T1 calculator
J Magn Reson, 177 (2): 212-220 (декабря 2005)
DOI: 10.1016/j.jmr.2005.07.022
Аннотация
The physics of spin–rotation interaction in roughly spherical perfluorinated gas molecules has been studied extensively. But, it is difficult to calculate a spin–lattice relaxation time constant T1 for any given temperature and pressure using the published literature. We give a unified parameterization that makes use of the Clausius equation of state, Lennard-Jones collision dynamics, and a formulaic temperature dependence for collision cross section for rotational change. The model fits T1s for SF6, CF4, C2F6, and c-C4F8 for temperatures from 180 to 360 K and pressures from 2 to 210 kPa and in mixtures with other common gases to within our limits of measurement. It also fits previous data tabulated according to known number densities. Given a pressure, temperature, and mixture composition, one can now calculate T1s for common laboratory conditions with a known accuracy, typically 0.5%. Given the success of the model’s formulaic structure, it is likely to apply to even broader ranges of physical conditions and to other gases that relax by spin–rotation interaction.
