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Register a new userMeasurement of the lifetime of the $7s^2S_{1/2} $ state in atomic cesium using asynchronous gated detection
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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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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.
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.
We report measurements of the Stark shift of the cesium $6s : ^2S_{3/2} rightarrow 7p : ^2P_{3/2} $ and the $6s : ^2S_{1/2} rightarrow 7p : ^2P_{1/2} $ transitions at $lambda = 456$ nm and 459 nm, respectively, in an atomic beam. From these, we determine the static scalar polarizability for both 7P states, and the tensor polarizability for the 7P$_{3/2}$ state. The fractional uncertainty of the scalar polarizabilites is $sim$0.18%, while that of the tensor term is 0.66%. These measurements provide sensitive tests of theoretical models of the Cs atom, which has played a central role in parity nonconservation measurements.
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 report measurements of the electric dipole matrix elements of the $^{133}$Cs $ $ $6s,^2S_{1/2} rightarrow 7p,^2P_{1/2}$ and $6s,^2S_{1/2} rightarrow 7p,^2P_{3/2}$ transitions. Each of these determinations is based on direct, precise comparisons of the absorption coefficients between two absorption lines. For the $langle 6s,^2S_{1/2}||r|| 7p,^2P_{3/2} rangle$ matrix element, we measure the ratio of the absorption coefficient on this line with that of the D$_1$ transition, $6s,^2S_{1/2} rightarrow 6p,^2P_{1/2}$. The matrix element of the D$_1$ line has been determined with high precision previously by many groups. For the $langle 6s,^2S_{1/2}||r|| 7p,^2P_{1/2} rangle$ matrix element, we measure the ratio of the absorption coefficient on this line with that of the $6s,^2S_{1/2} rightarrow 7p,^2P_{3/2}$ transition. Our results for these matrix elements are $langle 6s,^2S_{1/2}||r|| 7p,^2P_{3/2} rangle = 0.57417 : (57)~a_0$ and $langle 6s,^2S_{1/2}||r|| 7p,^2P_{1/2} rangle = 0.27810 : (45)~a_0$. These measurements have implications for the interpretation of parity nonconservation in atoms.
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