Hyperfine structure studies in the 6s 6p3P2-level of barium

Abstract

Abstraet. The hfs of the 3P 2 state of the 6s 6p configuration of atomic barium has been determined for 137Ba, applying the collinear fast-beam laser spectroscopy. The data fill the last gap in the experimental information on low lying 6s 2, 6s 6p, 6s 5d and 6p 5d configurations of this alcaline earth system. The results are analyzed in terms for the existing semi-empirical modified Breit-Wills theory (MBWT), working with two basic wave functions, as well as by an extension to six-component wave functions of inclusion of configuration interaction. The semi-empirical approaches lead to a consistent description of the different hyperfine structures; they are compared with the results from recent ab initio multiconfiguration Dirac Fock calculations. PACS: 31.30.G; 35.10.F According to recent multi-configuration Dirac Fock (MCDF) calculations strong configuration-mixing is expected in the 6s 6p and 6p 5d levels of atomic barium [6]. For an explicit treatment of this influence on the hfs we made efforts to extend the modified Breit-Wills theory (MBWT) to a basis of six states.In this semi-empirical approach the interval factors for magnetic dipole and electric quadrupole interaction A and B of altogether 14 states have been fitted to the now completed experimental basis. They are compared to the results from ab initio calculations. In spite of a number of simplifications which had to be introduced for reduction of the number of parameters entering and for ease of interpretation, the approximation gives a consistent description of most of these states including the effects of configuration interaction.