Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect

Abstract

We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole-dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d , n i , of both atoms. While for symmetric atom pairs with = = n n n d i 0 the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive-for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantummechanical effect, which points towards existence of optimal (we call them 'Tom' and 'Jerry' for 'big' and 'small') pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom-Jerry pairs with > > n n n i d 0 which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0 . We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom-Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate.

Autoionization widths of cold Rydberg atomic complexes

“…This chapter includes an analysis of PI effects in a cold Rydberg gas of sodium atoms. The accuracy of our presented below numerical results, based on the semi-classical approach, is better than 15% (Efimov et al, 2016). Fig.…”

“…Growth of Penning ionization rates (Γ) during diffusion of the atomic population. The black-body radiation-induced ionization rate W BBR (Efimov et al, 2016) is exhibited as a solid line as well.…”

“…Therefore, PI specifics identification is related to the analysis ofΓ N behavior in various quantum configurations N of atomic pairs. Publication Bezuglov & Borodin (1999) suggests simple quasi-classical formulas for calculating radiation constants of optical transitions in alkali-metal atoms, which were used in the surveys of PI autoionization widthsΓ N for symmetric pairs (n d = n i ) of rubidium atoms (Amthor et al, 2009) and asymmetric pairs (n d = n i ) of hydrogen atoms (Efimov et al, 2016). This chapter includes an analysis of PI effects in a cold Rydberg gas of sodium atoms.…”

Dynamic Instability of Rydberg Atomic Complexes

“…Equations (17), (18) result in the oscillation of the action δI with the maximum amplitude maxδI 2~4 K/π corresponding to the maximum distance between two separatrix branches that are generated in the phase space by Equation (7) [27]. We may assess the amplitudes δε of the energy oscillations of the resonance states that are depicted in Figure 6 as δε ≈|ω(I)|•max|δI|.…”

“…Under certain conditions, cold Rydberg media quickly evolve into cold neutral plasma, which is accompanied by the formation of free electrons and the development of various phenomena, such as spontaneous plasma expansion, recombination of Rydberg atoms, plasma instabilities, and the propagation of collective waves [12]. The physics of ultra-low-temperature plasma should take into account not only traditional ionization and recombination processes involving electrons and ions [13,14], but also the formation of charged particles, which are both due to the ionization of 2 of 19 Rydberg atoms by thermal radiation [12,15] and as a result of the Penning autoionization of Rydberg atomic pairs [16,17].…”