title: 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.
authors.affiliation: Centre for Quantum Technologies, National University Singapore, Singapore 117543.
authors.forename: Tarun
authors.initials: T
authors.lastname: Dutta
authors.affiliation: Centre for Quantum Technologies, National University Singapore, Singapore 117543.
authors.forename: Debashis
authors.initials: D
authors.lastname: De Munshi
authors.affiliation: Centre for Quantum Technologies, National University Singapore, Singapore 117543.
authors.forename: Dahyun
authors.initials: D
authors.lastname: Yum
authors.affiliation: Centre for Quantum Technologies, National University Singapore, Singapore 117543.
authors.forename: Riadh
authors.initials: R
authors.lastname: Rebhi
authors.affiliation: Centre for Quantum Technologies, National University Singapore, Singapore 117543.|Department of Physics, National University Singapore, Singapore 117551.|MajuLab, CNRS-UNS-NUS-NTU International Joint Research Unit, UMI 3654, Singapore.
authors.forename: Manas
authors.initials: M
authors.lastname: Mukherjee