Trilobites, butterflies, and other exotic specimens of long-range Rydberg molecules

Abstract

This Ph.D. tutorial discusses ultra-long-range Rydberg molecules, the exotic bound states of a Rydberg atom and one or more ground state atoms immersed in the Rydberg electron's wave function. This novel chemical bond is distinct from an ionic or covalent bond, and is accomplished by a very different mechanism: the Rydberg electron, elastically scattering off of the ground state atoms, exerts a weak attractive force sufficient to form the molecule in long-range oscillatory potential wells. In the last decade this topic has burgeoned into a vibrant and mature subfield of atomic and molecular physics following the rapidly developing capability of experiment to observe and manipulate these molecules. This tutorial focuses on three areas where this experimental progress has demanded more sophisticated theoretical descriptions: the structure of polyatomic molecules, the influence of electronic and nuclear spin, and the behavior of these molecules in external fields. The main results are a collection of potential energy curves and electronic wave functions which together describe the physics of Rydberg molecules. Additionally, to facilitate future progress in this field, this tutorial provides a general overview of the current state of experiment and theory.

Observation of spin-orbit-dependent electron scattering using long-range Rydberg molecules

“…Since their prediction almost twenty years ago [1] and boosted by their first observation [2], ultralong-range Rydberg molecules have become a research area of major interest (for reviews, see, e.g. [3][4][5]). Nevertheless, the spin substructure of these molecules is not fully understood yet.…”

Formation of ultracold ion pairs through long-range Rydberg molecules

“…In recent years, a solid understanding of the properties of long-range Rydberg molecules has been established and the developed theoretical tools explain experimental observations reliably, often even quantitatively [1,2]. Long-range Rydberg molecules are bound states of an atom in a Rydberg state and a ground-state atom within the orbit of the Rydberg electron.…”

Dressed Ion-Pair States of an Ultralong-Range Rydberg Molecule

“…The ULRM is a fragile dimer with a bond length ∼100 nanometers. This gargantuan molecule consists of a neutral perturber atom (B) bound to a highly excited Rydberg atom (A Ã ) [1][2][3][4]. The experimental observation of ULRMs [5][6][7] has led to their use in many diverse applications, e.g., as probes of chargeneutral interactions [8][9][10][11][12][13] or as impurities embedded in a many-body bath [14][15][16][17][18][19][20][21][22][23][24].…”

“…This framework requires as input only a set of atomic quantum defects μ l and scattering phase shifts δ L with l (LÞ indicating the electron's angular momentum relative to A þ (B). The generic scope of the GLFT approach permits us to include the effect of higher partial wave e − B scattering, avoiding the limitations of the Fermi-Omont pseudopotential or Green's function methods [3,25,26,[42][43][44][45][46]. The triplet e − B scattering phase shifts are obtained from a nonrelativistic two-electron R-matrix code [47,48].…”

“…(5) with a fitted nuclear quantum defect η J . of Δϵ on v with unity slope indicates that the nuclear states possess the proper Rydberg energy scaling, i.e., ΔE ∼ 1=v 3 . Figure 3(b) shows the same quantities as in 3(a) for the Σ "dragonfly" PEC.…”