The spin–rotation interaction in the van der Waals molecule KAr

Abstract

We report a study, by molecular beam methods, of the alkali–rare gas van der Waals molecule KAr. Paramagnetic potassium–argon molecules were produced in a supersonic molecular beam, and their magnetic hyperfine structure probed by resonance techniques. The principle interaction studied is the spin–rotational coupling of the spin angular momentum h/S of the alkali valence electron and the rotational angular momentum h/N of the molecule. The measured value of the interaction constant γ in the (v=0, N=0) molecular state is 240(10) kHz. Limits have been set on the variation of γ with R, the internuclear separation, over the range R=9 to 13 bohr.