Ba+ Isotope shift studies in preparation of atomic parity violation measurement

Abstract

The Ba+ ion, has a structure of spectral lines similar to heavy single valence electron alkali atoms. It is precisely studied by laser spectroscopy in presence of several light fields in order to prepare for a measurement of atomic parity violation (APV). Measurements in heavy alkali earth ions (e.g. Ba+ and Ra+) permit the precise determination of the weak mixing (Weinberg) angle sin2θW with improvement over the previous best measurement in neutral Cs by a factor of 5 in a week of actual measurement time. The transition frequencies for the 6s2S1/2 - 6p2P1/2, 6p2P1/2 - 5d2D3/2 and 6s2S1/2 - 5d2D3/2 transitions in 138Ba+ have been measured to 10−10 relative accuracy employing a line shape model for single ions in a radio frequency Paul trap [1]. These measurements have been extended to 134,136Ba+. Together with a determination of the lifetime of the excited 5d2D5/2 state these measurements provide for a stringent test of calculations, the accuracy of which is pivotal for a determination of sin2θW. The observed lifetime is 25.8(5)s. Being about 5s shorter than previous measurements and calculations agreeing with them, it provides for a puzzle. [1] E. A. Dijck et al., Phy. Rev. A 91, 060501(R)(2015)