Inconsistencies between lifetime and polarizability measurements in Cs

Abstract

Electric-dipole matrix elements for 6p −nd, n = 5, 6, 7 transitions in cesium are calculated using a relativistic all-order method. The resulting matrix elements are used to evaluate 5d lifetimes and 6p polarizabilities. The data are compared with experimental lifetime and polarizability measurements made by different groups. Domination of the 6p scalar polarizabilities by 5d − 6p dipole matrix elements facilitates an exacting consistency check of 5d lifetime and 6p polarizability data. Values of 5d − 6p matrix elements obtained from experimental 5d lifetime data are found to be inconsistent with those inferred from 6p polarizabilities derived from experimental Stark shift data. Our ab initio calculated 6p polarizabilities agree well with experimental determinations.PACS numbers: 31.15. Ar, 32.70.Cs, 32.10.Dk, 31.15.Dv The understanding of the accuracy of ab initio calculations in cesium is vital for the analysis of the Cs parity nonconservation (PNC) experiment [1]. In 1999, motivated by a number of recent high-precision experiments, Bennett and Wieman [2] reanalyzed the agreement of theoretical calculations and experimental data for a number of Cs atomic properties and reduced the previous theoretical uncertainty in the PNC amplitude by a factor of two. Utilizing measurements of the tensor transition polarizability, β, reported in same work, they demonstrated a 2.5σ discrepancy between the value of the weak charge Q W predicted by the Standard Model and that derived from the Cs PNC experiment. Although several papers (for example, [3,4,5,6,7,8,9]), have addressed this disagreement since 1999, the issue of the accuracy of ab initio calculations in Cs continues to be of interest.In this work, we investigate the radiative properties of Cs 6p − nd transitions. Although these do not bear directly on PNC experiments done to date, they have been the subject of careful experimental investigation, and thus provide benchmarks for precise comparison of theory and experiment. In particular, there exist two independent measurements of the lifetimes of the 5d states [10,11], which do not agree within their stated uncertainties. There also exist several experimental determinations of the 6p − 6s Stark shifts which allow to infer the values of polarizabilities of the 6p states [12,13,14]. Here we show that ab initio theory can check the mutual consistency of 5d lifetime and 6p polarizability data, with an accuracy of about 1%. We find the lifetime and polarizability results to be inconsistent at this level. Our calculations agree with the experimental values of 6p polarizabilities, but deviate from both determinations of the 5d lifetimes. We suggest that further experiments are desirable in order to clarify this issue. In addition, * Electronic address: msafrono@physics.udel.edu; Current address: Department of Physics and Astronomy, University of Delaware, Newark, Delaware, 19716 understanding of the accuracy of the 5d state properties in Cs is germane to the ongoing PNC experiment in isoelectronic Ba + [15], since the ...

All-Order Methods for Relativistic Atomic Structure Calculations

“…For example, the experimental values of the Stark shift of the 6s − 6p 1/2 and 6s − 6p 3/2 lines and lifetimes of the 5d j states in Cs were checked for consistency in Ref. [59]. From the standpoint of experiment, these are unrelated data produced by entirely different techniques.…”

“…Therefore, it is possible to cross-check these two experiments with minimal (and well understood) theoretical input by deriving 5d − 6p matrix elements from lifetime data, substituting them into the polarizability calculations, and comparing the results with experimental Stark shift values. This procedure was used in [59] to demonstrate that the Stark shift and lifetime data differed by 3-4σ.…”

“…The static scalar polarizabilities of the 6p j states and tensor polarizability of 6p 3/2 state in Cs were calculated in Ref. [59], and the scalar and tensor polarizabilities of the 7d 3/2 , 7d 5/2 , 9d 3/2 , 9d 5/2 , 10d 3/2 , and 10d 5/2 states of Cs were reported in Ref. [52].…”

“…All-order 1248 [59] 6867 ( ground state static polarizabilities of alkali-metal atoms. The term α vc 0 is very small and is calculated in either DHF or RPA approximation.…”

Black-body radiation shifts and theoretical contributions to atomic clock research

“…We note that this procedure is equivalent to scaling of the correlation potential in the PTSCI approach discussed in Section III-C. We conduct scaling starting from both LCCSD and LCCSDpT approximations. The scaling factors for the LCCSD and LCCSDpT calculations are different, and we take scaled LCCSD values to be our final results based on comparisons of similar calculations in alkali-metal atoms with experiments [39], [40], [41]. The uncertainty evaluation of the reduced matrix elements that give significant contributions to the polarizabilities is illustrated in Table IV, scaled values are listed with subscript "sc".…”