Rotational Magnetic Moments

Abstract

The presence in molecular-beam magnetic resonance of transitions with $\ensuremath{\Delta}m\ensuremath{\gg}1$ 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 $^{1}\ensuremath{\Sigma}$ 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\ifmmode\pm\else\textpm\fi{}0.00005; OCS, -0.02889\ifmmode\pm\else\textpm\fi{}0.00002; C${\mathrm{S}}_{2}$, (-)0.02274\ifmmode\pm\else\textpm\fi{}0.00002; ${\mathrm{C}}_{2}$${\mathrm{H}}_{2}$, -0.04903\ifmmode\pm\else\textpm\fi{}0.00004; Fe${(\mathrm{CO})}_{5}$, 0.0210\ifmmode\pm\else\textpm\fi{}0.0005; Ni${(\mathrm{CO})}_{4}$, 0.0179\ifmmode\pm\else\textpm\fi{}0.0005; C${\mathrm{F}}_{4}$, 0.031\ifmmode\pm\else\textpm\fi{}0.005. The sign of ${g}_{J}$ in ${\mathrm{C}}_{2}$${\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\ifmmode\pm\else\textpm\fi{}0.01 kc/sec.