High Precision Measurement of the Static Dipole Polarizability of Cesium

Abstract

The cesium 6 2 S 1/2 scalar dipole polarizability α 0 has been determined from the time-of-flight of laser cooled and launched cesium atoms traveling through an electric field. We find α 0 = 6.611 ± 0.009 × 10 −39 Cm 2 /V = 59.42 ± 0.08 × 10 −24 cm 3 = 401.0 ± 0.6 a 3 0 . The 0.14% uncertainty is a factor of fourteen improvement over the previous measurement. Values for the 6 2 P 1/2 and 6 2 P 3/2 lifetimes and the 6 2 S 1/2 cesium-cesium dispersion coefficient C 6 are determined from α 0 using the procedure of Derevianko and Porsev [Phys. Rev. A 65, 053403 (2002)].PACS numbers: 32.10. Dk,32.60.+i,32.70.Cs The static polarizability quantifies the effect of one of the simplest perturbations to an atom: the application of a static electric field inducing a dipole moment [1,2]. With increasing atomic number, relativistic effects [3,4] and core electron contributions [5,6] to the alkali polarizabilities become increasingly significant. In cesium, the heaviest stable alkali, the relativistic effects reduce the polarizability by 16% and the core contributes 4%. However, experimental uncertainties have made the measurements of the alkali polarizabilities relatively insensitive to the smaller core contribution, as shown in Fig 1. With the largest relativistic correction and core contribution of the stable alkali atoms, the cesium polarizability is an ideal benchmark for testing the theoretical treatment of both relativistic effects and core contributions. Our measurement advances the accuracy of the cesium polarizability by a factor of fourteen over the previous measurement [7] and places the uncertainty at 4% of the core contribution. [8] and [7], respectively, and (c) is this work. The contribution to the polarizability from the core electrons is expected to be smaller in Li than in Na. * Electronic address: JAMaddi@lbl.gov; Also at Physics Department, University California at Berkeley, Berkeley, CA 94720. † Electronic address: Gould@lbl.gov To our measurement's level of accuracy, the hyperfine levels of the cesium ground state have a common polarizability α 0 . From angular momentum relations [9], the dependencies of the polarizability on the hyperfine level F and on the magnetic sublevel M F are greatly suppressed in the cesium ground state. The small remaining dependencies, generated by the hyperfine interaction, have been measured in Refs. [10,11,12].For a static electric field E of moderate strength, the potential energy W of a neutral cesium atom in that field may be written in terms of α 0 as W = −(1/2)α 0 E 2 . All odd terms in E are disallowed by parity conservation and the linear term, also forbidden by time-reversal invariance, is experimentally known to be less than 1.6 × 10 −44 C-m in cesium [13]. The hyperpolarizability contribution, which scales as E 4 , has been calculated [14,15] and is negligible at the fields used for our measurement.Prior to the interferometric measurement of Ekstrom et. al. [8], the most accurate determinations of the alkali polarizabilities [7,16] had been made by measuring t...

Lifetime measurement of the cesium6P3/2level using ultrafast pump-probe laser pulses

“…and 6P 3/2 D 6S 1/2 = 6.339(3) a.u., agreeing with neither of the two theoretical studies to within the statistical uncertainties. In general the theoretical results align most closely with the indirect experimental techniques [24,25] as well as with ref. [23].…”

“…Our value falls between the two other direct measurements using position-correlated and timecorrelated photon counting, differing by 0.35% from that of Rafac et al [7] and by 0.17% from that of Young et al [23]. The indirect measurement results include those obtained from the value of the van der Waals C 6 coefficient deduced from high-resolution Feshbach spectroscopy [24]; from the Cs 6S 1/2 static dipole polarizability measured in an atomic fountain experiment [25]; [27,28] and from high-resolution spectroscopy of photoassociated cold atoms [27,28]. On average, the direct measurements give slightly higher lifetime values compared to the indirect techniques, although the measurement reported by Young et al [23] aligns well with the results of the indirect techniques.…”

“…Previous direct high-precision measurements of the Cs 6P 3/2 lifetime employed position-correlated photon counting in a fast Cs beam with a reported value of 30.57(7) ns [7] and time-correlated single-photon counting in a thermal Cs beam resulting in a value of 30.41 (10) ns [23]. Indirect methods have also obtained precise lifetimes of the 6P 3/2 state using the value of the van der Waals C 6 coefficient [24] and from the Cs 6S 1/2 static dipole polarizability [25]. Photoassociative molecular spectroscopy has also been used to extract atomic lifetimes with very small uncertainties, with a comprehensive review given by Bouloufa et al [26].…”

Ab initio studies of atomic properties and experimental behavior of element 119 and its lighter homologs

“…The calculated α, R max , and ΔH ads of group-1 elements are presented in Table I. The obtained α of Cs is in excellent agreement with the experimental value (401.0±0.6 [9]); similar accuracy can be expected from our predictions for Fr and element 119. For the neutral atoms, α (Fig.…”

Thermal and electrical properties of porphyrin derivatives and their relevance for molecule interferometry

“…The accuracy can be improved in future experiments: Calibrating the field and all geometric factors with atoms of known polarizability, such as cesium, 41 sodium, 40 or lithium, 42 will improve the field values to better than 1%.…”