Atoms,Moleeules ~~i~~:~ ~ D and Clusters

The hyperfine structure and isotope shift of 221- 226Ra and 212, 214Ra have been measured in the ionic (Ra 11) transition 7s 281/2- 7p 2P3/2 (2 = 381.4 nm). The method of on-line collinear fast-beam laser spectroscopy has been applied using frequency-doubling of cw dye laser radiation in an external ring cavity. The magnetic hyperfine fields are compared with semi-empirical and ab initio calculations. The analysis of the quadrupole splitting by the same method yields the following, improved values of spectroscopic quadrupole moments: Qs(221Ra) = 1.978(7)b, Qs(223Ra) = 1.254(3)b and the reanalyzed value