Hyperfine-structure calculations in XeII

The multiconfiguration Dirac-Fock model is employed to compute the hyperfin e interaction constants of the 5p(4)5d 4D(7/2), 5p(4)6p P-4(5/2), 5p(4)6p D -2(5/2) and 5p(4)6p D-4(7/2) levels of the xenon ion. The wavefunctions are obtained with the active space expansion method, where configuration stare functions of a specific parity and J value:are generated by substitutions from the reference configurations to an active set of orbitals. The active set is then increased in a systematic way, allowing the convergence of the expectation values to be monitored. The calculated electric field gradients are combined with experimentally determined electric quadrupole hyperfine constants in order to extract the nuclear electric quadrupole moment of iso tope 131 of Xe, for which the value Q = -0.117(6) barn is found.