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arXiv:1212.2990 · Physical Review A

Observation and analysis of resonant coupling between nearly degenerate levels of the 21Σg+ and 11Πg states of ultracold 85 Rb 2

Ryan Carollo, Michael Bellos, David Rahmlow, Jayita Banerjee, Edward E. Eyler, P. L. Gould, William C. Stwalley

Published Feb 13, 2013• 3 citations
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Abstract

We report on the anomalously high line strength of a single rotational level in the ultracold photoassociation of two ${}^{85}$Rb atoms to form ${}^{85}$Rb${}_{2}$. The ${v}^{\ensuremath{'}}=111$, ${J}^{\ensuremath{'}}=5$ level belongs to the Hund's case (c) $2\phantom{\rule{0.16em}{0ex}}({0}_{g}^{+})$ state, which correlates to the Hund's case (a) $2{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}_{g}^{+}$ state. Its strength is caused by coupling with a very near-resonant long-range state. The long-range component is the energetically degenerate ${v}^{\ensuremath{'}}=155$, ${J}^{\ensuremath{'}}=5$ level of the case (c) $2\phantom{\rule{0.16em}{0ex}}({1}_{g})$ state, correlating to the case (a) $1{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Pi}}_{g}$ state. The line strength is enhanced by an order of magnitude through this coupling, relative to nearby vibrational levels and even to nearby rotational levels of the same vibrational level. This enhancement is in addition to the enhancement seen in all ${J}^{\ensuremath{'}}=3$ and 5 levels of the $2\phantom{\rule{0.16em}{0ex}}({0}_{g}^{+})$ state due to an $l=4$ shape resonance in the $a{\phantom{\rule{0.16em}{0ex}}}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ state continuum, which alters the distribution of levels formed by photoassociation.

DOI
10.1103/physreva.87.022505

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Ultracold atomic physics offers an experimentalist the opportunity to perform sensitive tests and measurements that are not possible at higher temperatures. In this case it allows for access to molecular states, through photoassociation, that are inaccessible to conventional techniques. We use photoassociation to measure quasi-bound levels of the 2 1Σg+ state of 85Rb2 . With these data, we examine a coupling between the short-range Hund’s case (c) 2 (0g+ ) component and the long-range 2 (1g ) state, which corresponds to the 1 1Πg state. A second experiment studies the mechanism of short-range photoassociation and finds our simple model to have strong predictive power. In a third experiment, we photoassociatively form vibrationally excited a 3 Σu+ molecules. We then excite these molecules using a frequency-doubled pulse-amplified CW laser to create low-n long-range Rydberg states of 85Rb2 . Autoionization and ion detection of these states gives high-resolution spectra, which are compared to theoretical potential curves.
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