Precision measurement of the oscillator strength of the cesium 6S1∕22→5D5∕22 electric quadrupole transition in propagating and evanescent wave fields

Abstract

Hyperfine-structure-resolved absorption spectra of the $6\phantom{\rule{0.2em}{0ex}}^{2}S_{1∕2}\ensuremath{\rightarrow}5\phantom{\rule{0.2em}{0ex}}^{2}D_{5∕2}$ of cesium atoms have been observed with a temperature-controlled cell and a diode laser. From a comparison with the absorption of the ${D}_{2}$ transition at the same atom density range, the oscillator strength of the electric quadrupole transition was determined to be $(4.69\ifmmode\pm\else\textpm\fi{}0.05)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. Reflection spectra of the same transition have also been observed in the partial and total reflection regimes with a reflection cell. An increase in the apparent oscillator strength was observed for total reflection with an increase in the angle of incidence, by a factor up to 1.5 at ${\ensuremath{\theta}}_{c}+83.8\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}$ and 2.4 at ${\ensuremath{\theta}}_{c}+107.5\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}$ for $s$ and $p$ polarizations, respectively, where ${\ensuremath{\theta}}_{c}$ is the critical angle. The observed enhancement is ascribed to the incidence-angle-dependent wave vector and polarization vector of the evanescent wave.