Effect of photoions on the line shape of the Förster resonance lines and microwave transitions in cold rubidium Rydberg atoms

Abstract

Experiments are carried out on the spectroscopy of the Förster resonance lines Rb(37P) + Rb(37P) Rb(37S) + Rb(38S) and microwave transitions nP n'S, n'D between Rydberg states of cold rubidium atoms in a magneto optical trap (MOT). Under ordinary conditions, all spectra exhibit a linewidth of 2-3 MHz irrespective of the interaction time between atoms or between atoms and microwave radiation, although the limit resonance width should be determined by the inverse interaction time. The analysis of exper imental conditions has shown that the main source of line broadening is the inhomogeneous electric field of cold photoions that are generated under the excitation of initial nP Rydberg states by broadband pulsed laser radia tion. The application of an additional electric field pulse that rapidly extracts photoions produced by a laser pulse leads to a considerable narrowing of lines of microwave resonances and the Förster resonance. Various sources of line broadening in cold Rydberg atoms are analyzed.

Line shapes and time dynamics of the Förster resonances between two Rydberg atoms in a time-varying electric field

“…5(g) and 5(h) almost do not change with t. This means that the resonance takes its stationary form, and only its amplitude slowly grows with t according to Eq. (8). The resonance is cusp shaped, in agreement with Eq.…”

“…The dc electric field is calibrated with 0.2% uncertainty using the Stark spectroscopy of the microwave transition 37P 3/2 → 37S 1/2 at 80.124 GHz [6,8]. The MOT magnetic field is not switched off in order to have high repetition rate, but microwave probing on the same transition allowed us to align the excitation point to a nearly zero magnetic field [6].…”

“…In our earlier papers [6][7][8], we studied the line shape of the Förster resonance Rb(37P 3/2 ) + Rb(37P 3/2 ) → Rb(37S 1/2 ) + Rb(38S 1/2 ) in cold Rb Rydberg atoms excited by a broadband pulsed laser radiation via a three-photon transition. The resonance was recorded by slowly scanning a weak electric field near the resonant value of 1.79 V/cm [ Fig.…”

“…* ryabtsev@isp.nsc.ru However, an electric-field pulse was applied at the moment of laser excitation to pull out the cold Rb photoions formed due to photoionization by the intense pulsed laser radiation; otherwise, the Förster resonance became asymmetrical due to inhomogeneous electric fields from the photoions [8].…”

Dynamic Instability of Rydberg Atomic Complexes

“…Thus, for a "hydrogen-like" alkali metal atom with a standard [L-S] bond between the moments [33], the level {n, l + 1} may be located between the {n, l} and {n + 1, l} states of the excited atom (see Figure 1), which does not correspond to the case of the hydrogen atom [33]. In the case when the {n, l + 1} level is located exactly in the middle between the {n, l} and {n + 1, l} states, the Stark two-photon resonance condition is realized, otherwise the Förster resonance (hereinafter FR) [29] achieved in practice by an electric field of the order of 5 Vcm −1 [36]. The criterion for the emergence of the FR is simply formulated in terms of a quantum defect of atomic series:…”