Nuclear quadrupole moment of 139La from relativistic electronic structure calculations of the electric field gradients in LaF, LaCl, LaBr, and LaI.

Relativistic coupled cluster theory is used to determine accurate electric field gradients in order to provide a theoretical value for the nuclear quadrupole moment of (139)La. Here we used the diatomic lanthanum monohalides LaF, LaCl, LaBr, and LaI as accurate nuclear quadrupole coupling constants are available from rotational spectroscopy by Rubinoff et al. [J. Mol. Spectrosc. 218, 169 (2003)]. The resulting nuclear quadrupole moment for (139)La (0.200+/-0.006 barn) is in excellent agreement with earlier work using atomic hyperfine spectroscopy [0.20(1) barn].