A Precision Measurement of the Ratio of the NucleargValues ofLi7andLi6

Abstract

The molecular beam magnetic resonance method has been used to make a precision measurement of the ratio of the nuclear $g$ factors of ${\mathrm{Li}}^7$ and ${\mathrm{Li}}^6$. The central maximum of the ${\mathrm{Li}}^7$ line and the center of the ${\mathrm{Li}}^6$ line in the spectra of LiI and LiBr give the ratio $\frac{g_7}{g_6}$ to a precision limited only by experimental factors. The mean of eight independent determinations, under various experimental conditions, is 2.64094±0.00005. This value of the ratio is compared with that calculated by use of the Fermi formula from the known ratio $\frac{\Delta {\nu }_7}{\Delta {\nu }_6}$. The cube of the ratio of the reduced masses of the $2s$ electrons in ${\mathrm{Li}}^6$ and ${\mathrm{Li}}^7$ is included as a factor in the calculation by analogy with the corresponding case of the hydrogens. The observed value of $\frac{g_7}{g_6}$ is greater than the value calculated by (0.012±0.003) percent.