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Register a new userLifetime measurement of the 5d$^2$D$_{5/2}$ state in Ba$^+$
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The lifetime of the metastable 5d$^2$D$_{5/2}$ state has been measured for a single trapped Ba$^+$ ion in a Paul trap in Ultra High Vacuum (UHV) in the 10$^{-10}$ mbar pressure range. A total of 5046 individual periods when the ion was shelved in this state have been recorded. A preliminary value $tau_{D_{5/2}} = 26.4(1.7)$~s is obtained through extrapolation to zero residual gas pressure.
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We measure the lifetime of the cesium $5^2D_{5/2}$ state using a time-resolved single-photon-counting method. We excite atoms in a hot vapor cell via an electric quadrupole transition at a wavelength of $685,mathrm{nm}$ and record the fluorescence of a cascade decay at a wavelength of $852,mathrm{nm}$. We extract a lifetime of $1353(5),mathrm{ns}$ for the $5^2D_{5/2}$ state, in agreement with a recent theoretical prediction. In particular, the observed lifetime is consistent with the literature values of the polarizabilities of the cesium $6P$ states. Our measurement contributes to resolving a long-standing disagreement between a number of experimental and theoretical results.
We present a measurement of the branching fractions for decay from the long-lived $5D_{5/2}$ level in Ba. The branching fraction for decay into the $6S_{1/2}$ ground state was found to be $0.846(25)_{mathrm{stat}}(4)_{mathrm{sys}}$. We also report an improved measurement of the $5D_{5/2}$ lifetime, $tau_{5D_{5/2}}=31.2(0.9)$~s. Together these measurements provide the first experimental determination of transition rates for decay out of the $5D_{5/2}$ level. The low ($<7 times 10^{-12}$~Torr) pressure in the ion trap in which these measurements were made simplified data acquisition and analysis. Comparison of the experimental results with theoretical predictions of the transition rates shows good agreement.
Magneto-optically trapped atoms enable the determination of lifetimes of metastable states and higher lying excited states like the $rm{5d^{2}~^{3}F_{2}}$ state in barium. The state is efficiently populated by driving strong transitions from metastable states within the cooling cycle of the barium MOT. The lifetime is inferred from the increase of MOT fluorescence after the transfer of up to $30,%$ of the trapped atoms to this state. The radiative decay of the $rm{5d^{2}~^{3}F_{2}}$ state cascades to the cooling cycle of the MOT with a probability of $96.0(7),%$ corresponding to a trap loss of $4.0(7),%$ and its lifetime is determined to $rm{160(10)~mu s}$. This is in good agreement with the theoretically calculated lifetime of $rm{190~mu s}$ [J. Phys. B, {bf 40}, 227 (2007)]. The determined loss of $4.0(7),%$ from the cooling cycle is compared with the theoretically calculated branching ratios. This measurement extends the efficacy of trapped atoms to measure lifetimes of higher, long-lived states and validate the atomic structure calculations of heavy multi-electron systems.
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.
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.
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