An exacting transition probability measurement - a direct test of atomic many-body theories

Abstract

A new protocol for measuring the branching fraction of hydrogenic atoms with only statistically limited uncertainty is proposed and demonstrated for the decay of the P3/2 level of the barium ion, with precision below 0.5%. Heavy hydrogenic atoms like the barium ion are test beds for fundamental physics such as atomic parity violation and they also hold the key to understanding nucleo-synthesis in stars. To draw definitive conclusion about possible physics beyond the standard model by measuring atomic parity violation in the barium ion it is necessary to measure the dipole transition probabilities of low-lying excited states with a precision better than 1%. Furthermore, enhancing our understanding of the barium puzzle in barium stars requires branching fraction data for proper modelling of nucleo-synthesis. Our measurements are the first to provide a direct test of quantum many-body calculations on the barium ion with a precision below one percent and more importantly with no known systematic uncertainties. The unique measurement protocol proposed here can be easily extended to any decay with more than two channels and hence paves the way for measuring the branching fractions of other hydrogenic atoms with no significant systematic uncertainties.

Measurements of the branching ratios for 6P1/2 decays in Ba+138

“…It is also worth noting that branching ratios for decays from the P 3/2 level can be written entirely in terms of the ratios R 0 = 6P 3/2 r 6S 1/2 / 6P 1/2 r 6S 1/2 , R 1 , R 2 , and p. Consequently these can also be accurately estimated. For decays to S 1/2 , D 3/2 and D 5/2 , we estimate probabilities of 0.7428(6), 0.0279(1), and 0.2293(6), respectively, which are in disagreement with [8] at the level of ∼ 2 − 4 times the reported measurement uncertainties. Given that the experimental value of R 0 = 1.4140 (17) is also in disagreement with the theoretical estimate of 1.4109(2), it would be of interest to have an independent assessment of all measurements.…”

“…To computek k requires the recursively defined functions P m (t) = t 0 P m−1 (t − x)P 0 (x)dx, P 0 (t) = P (t), (8) which give the probability distributions for the emission time of the m + 1 photon following any given emission event. For each case the probability the detection time is within the dead time is…”

Observational constraints on the origin of the elements

“…For the combined terms, the lines were merged and the transition probabilities co-added as described in Bergemann et al (2012a). The oscillator strengths of the four diagnostic lines we used were extracted from the experimental transition probabilities presented in the studies by De Munshi et al (2015) and Dutta et al (2016). In total, the model contains 284 spectral lines in the wavelength range from 1330 to 202 930 Å.…”

Magic wavelength of the Ba+138 6s S1/

“…Together with previously determined matrix elements and branching ratios, this tightly constrains the dynamic differential scalar polarizability of the clock transition over a large wavelength range ( 700 nm). In particular it allows an estimate of the blackbody radiation shift of the clock transition at room temperature.PACS numbers: 06.30.Ft, 06.20.fb Singly-ionized barium has been well studied over the years with a wide range of precision measurements [1][2][3][4][5][6][7][8] that have provided valuable benchmark comparisons for theory [9][10][11][12][13][14]. It was recently proposed that some of these measurements, specifically high accuracy measurements of transition matrix elements and branching ratios, could be used to construct an accurate representation of the dynamic differential scalar polarizability, ∆α 0 (ω) of the S 1/2 −D 5/2 clock transition over a large wavelength range [15].…”