Resonant quenching of Rydberg atomic states by highly polar molecules

Abstract

The results of theoretical studies of the resonant quenching and ion-pair formation processes induced by collisions of Rydberg atoms with highly polar molecules possessing small electron affinities are reported. We elaborate an approach for describing collisional dynamics of both processes and demonstrate the predominant role of resonant quenching channel of reaction for the destruction of Rydberg states by electron-attaching molecules. The approach is based on the solution of the coupled differential equations for the transition amplitudes between the ionic and Rydberg covalent terms of a quasimolecule formed during a collision of particles. It takes into account the possibility of the dipole-bound anion decay in the Coulomb field of the positive ionic core and generalizes previous models of charge-transfer processes involving Rydberg atoms to the cases, when the multistate Landau-Zener approaches become inapplicable. Our calculations for ( ) nl Rb atom perturbed by C H SO 2 4 3 , CH CHCN 2 , CH NO 3 2 , CH CN 3 , C H O 3 2 3 , and C H O 3 4 3molecules show that the curves representing the dependence of the resonant quenching cross sections on the principal quantum number n are bell-shaped with the positions of maxima being shifted towards lower values of n and the peak values, ( ) s max q , several times higher than those for the ion-pair formation, ( ) s max i . We obtain a simple power relation between the energy of electron affinity of a molecule and the position of maximum in n-dependence of the resonant quenching cross section. It can be used as an additional means for determining small binding energies of dipole-bound anions from the experimental data on resonant quenching of Rydberg states by highly polar molecules.

Very strong Rydberg atom scattering in K(12p)–CH3NO2 collisions: Role of transient ion pair formation

“…Given that the size of the ion signals observed when detecting K + product ions was similar to the size of those seen using SF 6 at a similar target gas density, the data suggest that the rate constant for Rydberg atom scattering is sizable and much larger than what might be expected for simple ion-neutral scattering in a binary K + -CH 3 NO 2 collision, ∼10 −9 cm 3 s 1 . A large reaction rate, however, is consistent with recent theoretical studies by Lebedev and co-workers 35,36,43 of resonant quenching in Rydberg collisions with highly polar molecules through reactions of the type K(12p) + AB → K + + AB − * → K(n ) + AB. (4) In their discussion of resonant quenching, Lebedev and coworkers consider the transition amplitudes between the covalent K(12p)-CH 3 NO 2 and ionic K + -(dipole bound)CH 3 NO − 2 terms in the quasi-molecule formed during collisions.…”

“…(4) In their discussion of resonant quenching, Lebedev and coworkers consider the transition amplitudes between the covalent K(12p)-CH 3 NO 2 and ionic K + -(dipole bound)CH 3 NO − 2 terms in the quasi-molecule formed during collisions. (Since the binding energy of a dipole-bound CH 3 NO − 2 ion is expected to be ∼13 meV, 43 the crossing between the covalent K(12p)-CH 3 NO 2 and K + -(dipole bound)CH 3 NO − 2 potential curves occurs at a separation R c ∼ 200 a.u. which is similar in size to the radius of a K(12p) atom and in the region where the Rydberg electron probability density is maximum.)…”

Special Issue on Rydberg atom physics

“…In Fernandez et al, the formation of triatomic ultralong range molecules is theoretically explored in the presence of an electric field that modifies the molecular properties [27]. The paper by Narits et al [28] investigates how a Rydberg state can be perturbed by intermediate sized molecules. Although these latter systems are not currently possible to explore experimentally at ultracold temperatures, the study of these types of exaggerated systems is nevertheless intriguing.…”