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.
Highlights
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%
This particular ion has astrophysical importance due to its excessive abundance in certain main sequence stars which is popularly known as the barium puzzle[9,10]
These branching fractions are constrained as f51 + f52 + f53 = 1
Summary
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%. The possibility of directly measuring the population in lower atomic states after being excited to the higher state with nearly 100% efficiency on a single ion has allowed measurement of the branching fraction to below 1% in Ca+13 This technique in principle can be used for barium where the required precision is below 1%. It requires an extra laser and the precision is limited by the ability to transfer population to the excited state in a series of short laser pulses deterministically This technique requires a single ion and gathering statistics is time consuming. We propose and implement a new technique which can provide the robustness of photon counting as well as low uncertainties dominated only by measurement statistics
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