Electric dipole matrix elements for the $6p\ ^2P_J \rightarrow 7s\ ^2S_{1/2}$ transitions in atomic cesium*

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 $R=1.5270 \ (27)$, and the accuracy of our 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 measurement of the lifetime of the $7s\,^2S_{1/2}$ state, we determine reduced dipole matrix elements for $\langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{3/2} \rangle$ and $\langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{1/2} \rangle$. These matrix elements are also in excellent agreement with theoretical calculations. Measurements like these improve knowledge of Cs properties needed for parity violation studies and provide benchmark