Precise measurement of the scalar polarizability of $^{115}$In within the $5P_{1/2} \rightarrow 6S_{1/2}$ transition using an atomic beam*

In recent years, we have pursued a series of precise atomic structure measurements in Group III elements---currently thallium and indium - in order to test recent \emph{ab initio} theory calculations in these three-valance-electron systems. Such high-accuracy theory is essential for atomic physics-based tests of symmetry violation in these high-Z systems. We have recently completed a precision measurement of the indium scalar polarizability within the 410 nm $5P_{1/2} \rightarrow 6S_{1/2}$ transition using a GaN semiconductor laser interacting transversely with a collimated indium atomic beam in the presence of a large, precisely-calibrated electric field. We use laser frequency modulation and lock-in detection to obtain a high-resolution absorption signal despite indium beam optical depths of $< 0.001$. Our result for the indium scalar polarizability within this transition is 1000.2$\pm$2.7 in atomic units, and is in excellent agreement with a new atomic theory calculation\footnote{M.S. Safranova, private communication}. By combining the experimental result and theory expressions, new, precise values for the indium 6P-state lifetimes can be extracted. Details of the measurement and future plans will be presented.