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Register a new userEnhanced spin-dependent parity non-conservation effect in the $7s {}^2S_{1/2} to 6d {}^2D_{5/2}$ transition in Fr: A possibility for unambiguous detection of nuclear anapole moment
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Employing the relativistic coupled-cluster method, comparative studies of the parity non-conserving electric dipole amplitudes for the $7s ^2S_{1/2} rightarrow 6d ^2D_{5/2}$ transitions in $^{210}$Fr and $^{211}$Fr isotopes have been carried out. It is found that these transition amplitudes, sensitive only to the nuclear spin dependent effects, are enhanced by more than 3 orders compared to the low-lying $S-D_{5/2}$ transitions in Ba$^+$ and Ra$^+$ owing to the very large contributions from the electron core-polarization effects in Fr. This translates to a relatively large and, in principle, measurable induced light shift, which would be a signature of nuclear spin dependent parity nonconservation that is dominated by the nuclear anapole moment in a heavy atom like Fr. A plausible scheme to measure this quantity using the Cyclotron and Radioisotope Center (CYRIC) facility at Tohoku University has been outlined.
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Using recent high-precision measurements of electric dipole matrix elements of atomic cesium, we make an improved determination of the scalar ($alpha$) and vector ($beta$) polarizabilities of the cesium $6s ^2S_{1/2} rightarrow 7s ^2S_{1/2} $ transition calculated through a sum-over-states method. We report values of $alpha = -268.82 (30) a_0^3$ and $beta = 27.139 (42) a_0^3$ with the highest precision to date. We find a discrepancy between our value of $beta$ and the past preferred value, resulting in a significant shift in the value of the weak charge $Q_w$ of the cesium nucleus. Future work to resolve the differences in the polarizability will be critical for interpretation of parity non-conservation measurements in cesium, which have implications for physics beyond the Standard Model.
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.
We report a measurement of the ratio of electric dipole transition matrix elements of cesium for the $6p,^2P_{1/2} rightarrow 7s,^2S_{1/2}$ and $6p,^2P_{3/2} rightarrow 7s,^2S_{1/2}$ transitions. We determine this ratio of matrix elements through comparisons of two-color, two-photon excitation rates of the $7s,^2S_{1/2}$ state using laser beams with polarizations parallel to one another vs. perpendicular to one another. Our result of $R equiv langle 7s ^2S_{1/2} || r || 6p ^2P_{3/2} rangle / langle 7s ^2S_{1/2} || r || 6p ^2P_{1/2} rangle = 1.5272 (17)$ is in excellent agreement with a theoretical prediction of $R=1.5270 (27)$. Moreover, the accuracy of the experimental ratio is sufficiently high to differentiate between various theoretical approaches. To our knowledge, there are no prior experimental measurements of $R$. Combined with our recent determination of the lifetime of the $7s,^2S_{1/2}$ state, we determine reduced matrix elements for these two transitions, $langle 7s ^2S_{1/2} || r || 6p ^2P_{3/2} rangle = -6.489 (5) a_0$ and $langle 7s ^2S_{1/2} || r || 6p ^2P_{1/2} rangle = -4.249 (4) a_0$. These matrix elements are also in excellent agreement with theoretical calculations. These measurements improve knowledge of Cs properties needed for parity violation studies and provide benchmarks for tests of high-precision theory.
We report a measurement of the lifetime of the cesium $7s,^2S_{1/2}$ state using time-correlated single-photon counting spectroscopy in a vapor cell. We excite the atoms using a Doppler-free two-photon transition from the $6s,^2S_{1/2}$ ground state, and detect the 1.47$mu$m photons from the spontaneous decay of the $7s,^2S_{1/2}$ to the $6p,^2P_{3/2}$ state. We use a gated single photon detector in an asynchronous mode, allowing us to capture the fluorescence profile for a window much larger than the detector gate length. Analysis of the exponential decay of the photon count yields a $7s,^2S_{1/2}$ lifetime of 48.28$pm$0.07ns, an uncertainty of 0.14%. These measurements provide sensitive tests of theoretical models of the Cs atom, which play a central role in parity violation measurements.
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