Binary-collision-induced longitudinal relaxation in gas-phase 83Kr.

Density dependent NMR relaxation measurements of noble gases can provide complementary information to that obtained from relaxation studies of molecular gases. However, conventional noble gas NMR is typically hindered by low sensitivity or prohibitively long relaxation times. In this work, the low sensitivity of (83)Kr (I=92) was overcome by spin exchange optical pumping, and the quadrupolar interaction dominated (83)Kr T(1) times of 40-400 s enabled rapid collection of relaxation data. The density dependence of the (83)Kr longitudinal relaxation in pure krypton was found to be about 1.6 x 10(-3) amagat(-1) s(-1). Experiments were also performed in krypton mixtures containing either helium or nitrogen as a buffer gas. By varying the composition and the density of these mixtures, the density dependence of buffer gas induced relaxation and the relaxation efficiency of (83)Kr-buffer gas collisions were determined. The results from these gas mixtures are compared with those from pure krypton.