The
g factor of the $^{2}\ensuremath{\Sigma}$ Van der Waals molecule KAr has been measured relative to the
g factor of free potassium using molecular-beam magnetic-resonance techniques. A theoretical treatment of the
g factor of the molecule is presented that predicts the
g factor to be shifted from the value for the free potassium atom by an amount proportional to the ratio $\frac{\ensuremath{\gamma}}{B}$, where $\ensuremath{\gamma}$ and
B are the spin-rotational and rotational constants of the molecule, respectively. The experimental results show the molecular
g factor to be less than the value for free potassium by approximately 25 ppm, in agreement with the prediction.
Abstract The Van der Waals effect (VW) in 39K atomic vapours was experimentally studied using a nanocell made of technical sapphire. At distances of less than 100 nm from the sapphire surface, a strong broadening of atomic transitions and their frequency shifts to the low-frequency region of the spectrum occur. The method of selective reflection (SR) of laser radiation from the sapphire window-atomic vapours boundary was used as a sub-Doppler method, which made it possible to measure the VW interaction coefficient C3 for the potassium atoms. It is shown that a change in the nanocell thickness from 100 to 50 nm results in a decrease in C3, as calculated from the “red” VW shift, i.e., the so-called “retardation” of the VW effect, which was predicted in theoretical works and experimentally observed. The obtained results are important for the development of miniature submicron devices containing atomic vapours.
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.