Determination of spin–rotation interaction constants in fluorinated methane molecules by means of nuclear spin relaxation measurements

Abstract

The proton and fluorine spin relaxation time T₁ has been measured in CH₄, CF₄, CHF₃, and CH₃F gases at low densities. By measuring the dependence of T₁ on density near the characteristic T₁ minimum, new information has been obtained on the spin–rotation interaction coupling constants in CF₄, CHF₃, and CH₃F. The CH₄ system was used to test the validity of this method since the spin–rotation coupling constants are accurately known for CH₄. The correlation function for the spin–rotation interaction was found to be exponential within experimental error for all of the molecules studied. In the analysis of the experimental data, the effects of the dipolar interactions and of nuclear spin symmetry considerations were completely neglected. The validity of these approximations is discussed in the Appendix.