title: Inert fluorinated gas T1 calculator.
abstract: 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.
authors.affiliation: New Mexico Resonance, Albuquerque, NM, USA. dkuethe@nmr.org
authors.forename: Dean O
authors.initials: DO
authors.lastname: Kuethe
authors.forename: Tanja
authors.initials: T
authors.lastname: Pietrass
authors.forename: Volker C
authors.initials: VC
authors.lastname: Behr
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D005741:Noble Gases / Q000737:chemistry*; D011312:Pressure; D013696:Temperature
chemical_list: D005741:Noble Gases