The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of ${}^6{\mathrm{Li}}^{19}\mathrm{F}$ for the purpose of obtaining an improved value of the ratio of the electric quadrupole moments of the two lithium nuclei. A total of 29 transitions in vibrational states 0-2 and rotational states 1-4 have been included in a fit to determine the Li nuclear quadrupole interaction along with the magnetic spin-rotation and spin-spin interactions. The magnetic interactions are consistent with values calculated from the previously reported ${}^7{\mathrm{Li}}^{19}\mathrm{F}$ values, but those have been refitted to take advantage of the new information from ${}^6{\mathrm{Li}}^{19}\mathrm{F}$. The electric quadrupole moment ratio of the two lithium isotopes determined from measurements on the two forms of LiF is ${Q(}^6\mathrm{Li}{)/Q(}^7\mathrm{Li})=0.020161\mathrm{}\pm 0.000013$ (one standard deviation estimate).

• Received 7 October 1996

DOI:https://doi.org/10.1103/PhysRevA.57.2539