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Register a new userMeasurements of the branching ratios for $6P_{1/2}$ decays in $^{138}$Ba$^+$
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Measurement of the branching ratios for $6P_{1/2}$ decays to $6S_{1/2}$ and $5D_{3/2}$ in $^{138}$Ba$^+$ are reported with the decay probability from $6P_{1/2}$ to $5D_{3/2}$ measured to be $p=0.268177pm(37)_mathrm{stat}-(20)_mathrm{sys}$. This result differs from a recent report by $12sigma$. A detailed account of systematics is given and the likely source of the discrepancy is identified. The new value of the branching ratio is combined with a previous experimental results to give a new estimate of $tau=7.855(10),mathrm{ns}$ for the $6P_{1/2}$ lifetime. In addition, ratios of matrix elements calculated from theory are combined with experimental results to provide improved theoretical estimates of the $6P_{3/2}$ lifetime and the associated matrix elements.
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Branching fractions for decays from the $P_{3/2}$ level in $^{138}$Ba$^+$ have been measured with a single laser-cooled ion. Decay probabilities to $S_{1/2}$, $D_{3/2}$ and $D_{5/2}$ are determined to be $0.741716(71)$, $0.028031(23)$ and $0.230253(61)$, respectively, which are an order of magnitude improvement over previous results. Our methodology only involves optical pumping and state detection, and is hence relatively free of systematic effects. Measurements are carried out in two different ways to check for consistency. Our analysis also includes a measurement of the $D_{5/2}$ lifetime, for which we obtain 30.14(40),s.
Measurement of the $^{138}$Ba$^+$ ${}^2S_{1/2} - {}^2D_{5/2}$ clock transition frequency and $D_{5/2}$ Lande $g_J$ factor are reported. The clock transition frequency $ u_{mathrm{Ba}^+}=170,126,432,449,333.31pm(0.39)_mathrm{stat}pm(0.29)_mathrm{sys},$Hz, is obtained with accuracy limited by the frequency calibration of the maser used as a reference oscillator. The Land{e} $g_J$-factor for the ${}^2D_{5/2}$ level is determined to be $g_{D}=1.200,367,39(24)$, which is a 30-fold improvement on previous measurements. The $g$-factor measurements are corrected for an ac-magnetic field from trap-drive-induced currents in the electrodes, and data taken over a range of magnetic fields underscores the importance of accounting for this systematic.
The zero crossing of the dynamic differential scalar polarizability of the $S_{1/2}-D_{5/2}$ clock transition in $^{138}$Ba$^+$ has been determined to be $459.1614(28),$THz. 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 ($gtrsim 700,$nm). In particular it allows an estimate of the blackbody radiation shift of the clock transition at room temperature.
The branching fractions from the excited state $6P_{1/2}$ of singly charged barium ion has been measured with a precision $0.05%$ in an ion trap experiment. This measurement along with the known value of the upper state life-time allowed the determination of the dipole matrix elements for the transitions $P-S$ and $P-D$ to below one percent level. Therefore, for the first time it is now possible to compare the many body calculations of these matrix elements at level which is of significance to any parity non-conservation experiment on barium ion. Moreover, these dipole matrix elements are the most significant contributors to the parity violating matrix element between the $S-D$ transition, contributing upto $90%$ to the total. Our results on the dipole matrix elements are $3.306pm0.014$ and $3.036pm0.016$ for the $S-P$ and $P-D$ transitions respectively.
The WASA-at-COSY experiment has collected $3times10^{7}$ events with $eta$-mesons produced via the reaction $pdrightarrow{^{3}textrm{He}}eta$ at $textrm{T} = 1.0 textrm{GeV}$. Using this data set, we evaluate the branching ratios of the decays $etatopi^{+}pi^{-}gamma$, $etato e^{+}e^{-}gamma$, $etatopi^{+}pi^{-}e^{+}e^{-}$ and $etato e^{+}e^{-}e^{+}e^{-}$. The branching ratios are normalized to the $etarightarrowpi^{+}pi^{-}pi^{0}$ decay. In addition an upper limit on a $CP$-violating asymmetry in $etarightarrow pi^{+}pi^{-}e^{+}e^{-}$ is extracted.
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