ac electric-field-induced resonant energy transfer between cold Rydberg atoms

An oscillating electric field at 1.356 GHz was used to promote the resonant energy transfer process: $43d_{5\mathrm{/}2}+43d_{5\mathrm{/}2}\to 45p_{3\mathrm{/}2}+41f$ between translationally cold ${}^{85}$Rb Rydberg atoms. The ac Stark shifts due to this dressing field created degeneracies between the initial and final two-atom states of this process. The ac field strength was scanned to collect spectra which are analogous to dc electric-field-induced resonant energy transfer spectra. Different resonances were observed for different magnetic sublevels involved in the process. Compared to earlier work performed at higher frequencies, the choice of dressing frequency and structure of the spectra may be intuitively understood, by analogy with the dc field case.