An improved value of the nuclear quadrupole moment of the 197 keV I = 52 excited state of 19F

Highly correlated ab initio calculations of the electric field gradient at the fluorine nuclei in F2 have been carried out using large and accurate basis sets, yielding results close to the basis set limit. Combination of the experimentally determined quadrupole coupling constant for F2 and the calculated electric field gradient has led to a new value of the nuclear quadrupole moment of the I = 52 excited state at 197 keV of the 19F nucleus. The Q-value obtained is (−94.2 ± 0.9) × 10−31 m2 (millibarn (mb)), and this value is demonstrated to be significantly more accurate than the old standard value of −72 ± 4 mb based on self-consistent-field calculations on the FCl molecule.