Rotational Magnetic Moments

Abstract

The presence in molecular-beam magnetic resonance of transitions with $\Delta m\gg 1$ has made possible measurements of gyromagnetic ratios which are very much smaller than the nuclear magneton. Such low values are normally associated with the rotation of ${}_{}{}^1{}_{}{}^{}\Sigma$ molecules. The following values of $g_J$ in nuclear magnetons per rotational quantum number have been determined in this way: C${\mathrm{O}}_2$, (-)0.05508±0.00005; OCS, -0.02889±0.00002; C${\mathrm{S}}_2$, (-)0.02274±0.00002; ${\mathrm{C}}_2$ ${\mathrm{H}}_2$, -0.04903±0.00004; Fe${\mathrm{}\left(\mathrm{CO}\right)\mathrm{}}_5$, 0.0210±0.0005; Ni${\mathrm{}\left(\mathrm{CO}\right)\mathrm{}}_4$, 0.0179±0.0005; C${\mathrm{F}}_4$, 0.031±0.005. The sign of $g_J$ in ${\mathrm{C}}_2$ ${\mathrm{H}}_2$ has been found to be the same as that in OCS, which was known to be negative. The signs in parentheses are assumed. The technique also gives the spin-rotational interaction constant in ${\mathrm{C}}_2$ ${\mathrm{H}}_2$ as 3.58±0.01 kc/sec.