AC polarizability and photoionization cross-section measurements in an optical lattice

TL;DR

This paper measures the dynamic scalar polarizability and photoionization cross-section of rubidium's 5D_{3/2} level at 1064 nm using double-resonant two-photon spectroscopy in an optical lattice, providing new experimental data.

Contribution

The study introduces a spectroscopic method that determines polarizability without measuring light intensity and reports the first measurement of the photoionization cross-section at this wavelength.

Findings

Polarizability of -524(17) atomic units measured

Photoionization cross-section of 44(1) Mb determined

Method avoids direct light intensity measurement

Abstract

We use double-resonant two-photon laser spectroscopy to measure the dynamic scalar polarizability of the rubidium 5$D_{3/2}$ level, $\alpha^{S}_{5D_{3/2}}$, at a wavelength of $\lambda=1064$~nm. Since $\lambda$ is shorter than the photoionization (PI) limit of the Rb 5$D_{3/2}$ level, $\alpha^{S}_{5D_{3/2}}$ depends on both bound-bound and bound-free transition matrix elements. The level also undergoes significant broadening due to PI. The $1064$-nm field is applied in the form of a deep optical lattice ($\sim10^{5}$~photon recoils) generated by an in-vacuum field-enhancement cavity. In our spectroscopic method, we use known dynamic polarizabilities to eliminate the need to measure the light intensity. Our method yields, in atomic units, $\alpha^{S}_{5D_{3/2}}=-524(17)$, in agreement with estimates. Additionally, we extract the $5D_{3/2}$ photoionization cross section $\sigma$ at $1064$~nm from spectral linewidths; we find $\sigma=44(1)$~Mb.