Observation of Deeply-Bound $^{85}$Rb$_{2}$ Vibrational Levels Using Feshbach Optimized Photoassociation

TL;DR

This paper demonstrates Feshbach optimized photoassociation to observe deeply-bound vibrational levels in $^{85}$Rb$_{2}$, enabling measurement of levels previously inaccessible to traditional methods, with detailed resonance characterization.

Contribution

It introduces and experimentally validates Feshbach optimized photoassociation for measuring deeply-bound vibrational levels in ultracold molecules.

Findings

Observed three new vibrational levels with specific binding energies.

Measured resonance frequencies, magnetic field positions, and widths.

Confirmed the technique's ability to access levels below traditional spectroscopy.

Abstract

We demonstrate Feshbach optimized photoassociation (FOPA) into the $0_{g}^{-} (5$S$_{1/2}+5$P$_{1/2}$) state in $^{85}$Rb$_{2}$. FOPA uses the enhancement of the amplitude of the initial atomic scattering wave function due to a Feshbach resonance to increase the molecular formation rate from photoassociation. We observe three vibrational levels, $v=$127, 140, and 150, with previously unmeasured binding energies of 256, 154, and 96 cm$^{-1}$. We measure the frequency, central magnetic field position, and magnetic field width of each Feshbach resonance. Our findings experimentally confirm that this technique can measure vibrational levels lower than those accessible to traditional photoassociative spectroscopy.