We report a measurement of the ratio of electric dipole transition matrix elements of cesium for the 6p 2 P 1/2 → 7s 2 S 1/2 and 6p 2 P 3/2 → 7s 2 S 1/2 transitions. We determine this ratio of matrix elements through comparisons of two-color, two-photon excitation rates of the 7s 2 S 1/2 state using laser beams with polarizations parallel to one another vs. perpendicular to one another. Our result of R ≡ 7s 2 S 1/2 ||r||6p 2 P 3/2 / 7s 2 S 1/2 ||r||6p 2 P 1/2 = 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 2 S 1/2 state, we determine reduced matrix elements for these two transitions, 7s 2 S 1/2 ||r||6p 2 P 3/2 = −6.489 (5) a0 and 7s 2 S 1/2 ||r||6p 2 P 1/2 = −4.249 (4) a0. 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 2 S 1/2 state using time-correlated singlephoton counting spectroscopy in a vapor cell. We excite the atoms using a Doppler-free two-photon transition from the 6s 2 S 1/2 ground state, and detect the 1.47 µm photons from the spontaneous decay of the 7s 2 S 1/2 to the 6p 2 P 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 2 S 1/2 lifetime of 48.28 ± 0.07 ns, 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. PACS numbers: 32.70.CsPrecision laboratory measurements of electric dipole (E1) matrix elements are critical for the advancement of atomic parity violation (PV) studies in several regards: Precise models of atomic structure are required to extract the weak charge Q w from any measurement of the PV transition moment; E1 matrix elements are included explicitly in the perturbative expansion for the PV moment; and measurements of the PV amplitude are always carried out relative to a different optical transition amplitude, such as a Stark-induced amplitude. Thus, we require precise determinations of electric dipole matrix elements, through a variety of laboratory measurements, and detailed comparison with ab initio theoretical results.The most precise determination of a PV moment in any atomic system is that of the 6s 2 S 1/2 → 7s 2 S 1/2 transition in cesium, carried out by Wood et al. in 1997 [1]. In the past 30 years, several advances in models of the atomic structure of the cesium atom [2][3][4][5][6][7][8][9][10][11][12], and measurements of key transition amplitudes [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] have been reported. The uncertainty in the E1 transition moment 7s||r||6p 1/2 is presently one of the primary contributors, along with the 7p 1/2 ||r||6s matrix element, to the uncertainty in the PV moment for the 6s 2 S 1/2 → 7s 2 S 1/2 transition [11,23]. Similarly, the uncertainties in 7s||r||6p 1/2 and 7s||r||6p 3/2 are primary contributors to the uncertainty of the scalar Stark polarizability for the 6s → 7s transition [20,23].In this paper we present our measurement of the lifetime of the cesium 7s 2 S 1/2 state using an asynchronous time-correlated single-photon counting (TCSPC) technique. By measuring the lifetime of the 7s state, we indirectly measure the matrix elements named above. We find a lifetime value of 48.28 ± 0.07 ns, in good agreement with the previous measurement by Bouchiat et al.[13], but with much smaller uncertainty, and in agreement with several theoretical determinations [3-6, 9, 11]. This work paves the way to reducing the uncertainty of the PV transition amplitude and Stark polarizability, and complements progress we are making toward a new atomic PV measurement in cesium [24,28].Cesium atoms in t...

We report measurements of the hyperfine coupling constant for the 8p 2 P 1/2 level of atomic cesium, 133 Cs, with a relative uncertainty of ∼0.019%. Our result is A = 42.933 (8) MHz, in good agreement with recent theoretical results. We also examine the hyperfine structure of the 8p 2 P 3/2 state, and derive new values for the state energies of the 8p 2 P 1/2 and 8p 2 P 3/2 states of cesium.