### Session U4: Focus Session: Cold Rydberg Gases

10:30 AM–12:30 PM, Friday, June 17, 2011
Room: A704

Chair: Michael Noel, Bryn Mawr College

Abstract ID: BAPS.2011.DAMOP.U4.4

### Abstract: U4.00004 : Dipole-dipole broadening of \textit{ns-np} Rydberg transitions

11:42 AM–11:54 AM

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#### Authors:

Hyunwook Park
(University of Virginia)

Tom Gallagher
(University of Virginia)

Using a microwave resonance technique we have measured the dipole-dipole broadening of \textit{ns-np} transitions of 300\textit{$\mu$K} Rb Rydberg atoms. The experiment has been done with $n$=28, 29, 34, 39, 44, and 50 states, all of which exhibit a linear increase in the linewidth with atomic density. The broadening rate varies as $n^{4}$, which is to be expected since \textit{$\mu$}$_{sp}\approx n^{2}$. The broadening is not Lorentzian, but results in asymmetric, cusp shaped resonances. To reproduce the observed resonances we have developed a molecular model in which pairs of atoms are driven from the \textit{nsns} to the \textit{nsnp/npns} states, which have a dipole-dipole energy splitting which scale as 1/R$^{3}$. We calculate the dipole-dipole splitting of the \textit{nsnp/npns} states, and the transition strengths from the nsns states with the spins of the two electrons included. The results, averaged over the density of Rydberg atoms, yield asymmetric cusp shaped resonances, which agree very well with the observations.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.DAMOP.U4.4