Reviews of Modern Physics

Adventures of a Rydberg electron in an anisotropic world

William Clark, Chris H. Greene

Published Apr 1, 1999• 21 citations

Abstract

The study of subtle interactions in atomic and molecular systems has stirred scientific curiosity since the dawn of quantum mechanics. Even today, research into perturbative long-range interactions continues to push into new territory, driven largely by the experimental capabilities of Rydberg state spectroscopy to detect effects of extremely weak interactions. While static long-range multipole interactions have been studied for years, the presence of dynamic terms that involve both position and momentum operators has been demonstrated only surprisingly recently. In this paper we document the existence of an effective vector interaction term in the long-range potential experienced by a moving charged particle in the presence of an anisotropic ionic core. In contrast to ordinary static quadrupole or dipole interaction terms, the existence of this vector interaction hinges on the motion of the distant charge as it roams beyond the confines of the core.

DOI: 10.1103/revmodphys.71.821

Related papers

Rydberg states about dipolar cores: The quantum dynamics of the long-range anisotropic interaction

L. Ya. Baranov, F. Remacle, Raphael David Levine

High Rydberg states about a dipolar molecular core can exhibit special features due to the exceptionally long range of the electrical anisotropy of the core. Unlike all other, more localized, couplings of the Rydberg electron to the ion, here the interaction is not shielded by the centrifugal barrier. The influence of the core even on states of the electron with higher angular momentum l and the significant matrix elements between states that differ considerably in the principal quantum number n make this problem worthy of separate considerations. Using specialized computational techniques (both analytical and numerical) for the exact evaluation of the relevant matrix elements, the role of both inter- and intra-Rydberg series coupling is discussed. The importance of the latter (i.e., the coupling of the Rydberg electron to the rotation of the core) is emphasized. Special attention is given to the role of an external dc electrical field that is different in the present problem in that it does not significantly dilute the strength of the electron-core interaction. A positively charged core can have a dipole moment (defined with respect to its center of mass) larger than that of neutral polar molecules, particularly if the charge is localized. Hence the interseries and intraseries dynamics discussed in this paper can give rise to experimentally measurable special effects. \textcopyright{} 1996 The American Physical Society.

Physical Review ADec 1, 199621 citations

Rydberg atoms in ponderomotive potentials

Brenton Knuffman

In this thesis, we examine the ponderomotive interaction between an applied optical field and a highly excited Rydberg electron. An atom in a Rydberg state is essentially composed of an electron loosely bound, at a relatively large radial separation, to a positive ionic core. As such, the ponderomotive interaction for the Rydberg electron is similar to the interaction with free charges, which has been studied in context of plasma physics, new particle accelerator techniques, ion trapping, and electron diffraction among others. We are focused on using the ponderomotive interaction with the Rydberg electron to exert control over both the center-of-mass and electronic states of translationally cold Rydberg atoms. These capabilities can be adapted as tools for application in many experiments in areas such as atomic spectroscopy and quantum information processing. Our theoretical investigations have provided a well-defined parameter space for our experimental work and have allowed us to develop experimental methods appropriate for studying Rydberg atoms in ponderomotive potentials. In dense gases of cold Rydberg atoms, rich dynamics stem from electric multipole interactions among the Rydberg atoms. For example, interatomic forces between Rydberg atoms cause state-changing collisions which can significantly increase the kinetic energy of the colliding atoms. In addition to the studies of Rydberg atoms in ponderomotive potentials, we discuss collisions of cold Rydberg atoms in which internal energy of the Rydberg atoms is converted into kinetic energy.

Jan 1, 20090 citations

Long-range interactions in one- and two-electron Rydberg atoms

Christophe L. Vaillant

We present calculations of long-range interactions in Rydberg atoms, with a focus on the dipole-dipole interactions of strontium Rydberg states. The growing use of Rydberg states in the field of cold atoms necessitates a more detailed understanding of the effects of dipole-dipole interactions, which are currently being investigated in a number of research groups worldwide. Calculations of long-range interactions in Rydberg states of caesium, cal- cium, rubidium, strontium and ytterbium are presented. By taking the one active electron approximation we develop consistent models of these long- range interactions, and construct a survey of the Rydberg state dipole-dipole interactions and quadrupole-quadrupole interactions. We compare the inter- actions between series and between atoms, highlighting the importance of certain series for applications suggested in previous works. In order to include two-electron effects in the description of dipole-dipole interactions in divalent atoms, we use multichannel quantum defect theory (MQDT) to develop models of the Rydberg series of strontium. We use an empirical reactance matrix formalism, where the reactance matrix is fitted to reproduce experimentally measured values of the bound state energy levels. Models are found for all series of strontium with L ≤ 3. We extend the MQDT formalism to the description of the natural radiative lifetimes of strontium, where the perturbers are found to have a large quenching effect on these lifetimes. By incorporating the MQDT description of the Rydberg states of strontium into the calculation of dipole-dipole interactions, we find a spin-forbidden two-atom resonance in the 3D2 states of strontium. We consider a one- dimensional lattice of strontium atoms, and find that the internal dynamics of the Rydberg atoms demonstrates spin transport for large lattice spacings and a separation of the spin and total angular momentum dynamics for small lattice spacings. Spin-angular momentum separation (analogous to spin-charge separation in condensed matter) in strontium Rydberg atoms may have uses in the investigation of one-dimensional Fermi gases and their description using Luttinger liquid theory.

Jan 1, 20144 citations

Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. I. Long-range interaction effects in the ionic-covalent coupling

Владимир Сергеевич Лебедев, Alexander A. Narits

Ion-pair formation processes are studied in collisions of Rydberg atoms with neutral particles possessing small electron affinities. Nonadiabatic transitions from a Rydberg covalent term to an ionic term of a quasi-molecule are considered using the modified Landau-Zener theory supplemented with calculation of survival factors of an anion decaying in the Coulomb field of a positive ion core. Using the technique of irreducible tensor operators and the momentum representation of the wavefunction of a highly excited atom, exact expressions are obtained for transition matrix elements and the ionic-covalent coupling parameter. The approach developed in the paper provides the description beyond the scope of a conventional assumption about a small variation of the wavefunction of the Rydberg atom on the range of electron coordinates determined by the characteristic radius of the wavefunction of the anion. This allows one to correctly consider long-range effects of the interaction between a weakly bound electron and the neutral core of a negative ion in processes under study. It is shown by the example of thermal collisions of Xe( nf ) atoms with CH 3 CN molecules that this is very important for a reliable quantitative description of anion formation with a low binding energy. The results are compared with experiments and calculations performed within the framework of a number of approximate methods.

Journal of Experimental and Theoretical PhysicsOct 1, 20136 citations

Long-range interaction between polar Rydberg atoms

M. Raymond Flannery, D. Vrinceanu, Valentin N. Ostrovsky

The most attractive and the most repulsive potential-energy curves for interaction between two Rydberg atoms in a broad superposition of internal angular momentum states are studied. The extreme Stark states have the largest dipole moments and provide the dominant contribution to the interaction which is then expressed as a long-range expansion involving the permanent multipole moments Q j of each polar atom. Analytical expressions are obtained for all Q j associated with principal quantum number n of H( n ) and permit the long-range expansion for the H( n )–H( n ') first-order interaction to be explicitly expressed analytically in terms of n , n ' and internuclear distance R . Possible quasi-molecular formation is investigated. Direct calculations show that the H( n = 2)–H( n ' = 2) interaction is capable of supporting 47 bound vibrational levels. As n increases, the long-range interaction becomes increasingly attractive so that molecular formation at large internuclear distances is expected to be scarcely possible for these extreme Stark levels.

Journal of Physics B Atomic Molecular and Optical PhysicsJan 6, 200547 citations

Long-range interactions between Rydberg atoms

Johannes Deiglmayr

Abstract We present an overview over theoretical models to describe adiabatic potential-energy curves, experimental excitation spectra, and electronic and nuclear dynamics in interacting Rydberg-atom pairs at large internuclear separations. The potential-energy curves and molecular wavefunctions are determined from the multipole expansion of the static Coulomb interaction which is evaluated numerically in a product basis of atomic orbitals. The convergence of this approach both in the truncation of the multipole expansion as well as in the size of the product basis is discussed, and the comparison of simulated excitation spectra is established as a useful criterium to test the convergence of the calculation. We finally discuss the dynamics of electronic and nuclear motions of pairs of Rydberg atoms, focusing on the stability of ultralong range Rydberg molecules with respect to autoionization.

Physica ScriptaSep 22, 201620 citations