Observation of ultralong-range Rydberg molecules

Abstract

Rydberg atoms have an electron in a state with a very high principal quantum number, and as a result can exhibit unusually long-range interactions. One example is the bonding of two such atoms by multipole forces to form Rydberg-Rydberg molecules with very large internuclear distances. Notably, bonding interactions can also arise from the low-energy scattering of a Rydberg electron with negative scattering length from a ground-state atom. In this case, the scattering-induced attractive interaction binds the ground-state atom to the Rydberg atom at a well-localized position within the Rydberg electron wavefunction and thereby yields giant molecules that can have internuclear separations of several thousand Bohr radii. Here we report the spectroscopic characterization of such exotic molecular states formed by rubidium Rydberg atoms that are in the spherically symmetric s state and have principal quantum numbers, n, between 34 and 40. We find that the spectra of the vibrational ground state and of the first excited state of the Rydberg molecule, the rubidium dimer Rb(5s)-Rb(ns), agree well with simple model predictions. The data allow us to extract the s-wave scattering length for scattering between the Rydberg electron and the ground-state atom, Rb(5s), in the low-energy regime (kinetic energy, <100 meV), and to determine the lifetimes and the polarizabilities of the Rydberg molecules. Given our successful characterization of s-wave bound Rydberg states, we anticipate that p-wave bound states, trimer states and bound states involving a Rydberg electron with large angular momentum-so-called trilobite molecules-will also be realized and directly probed in the near future.

Ultralong-range Rydberg molecules in combined electric and magnetic fields

“…A prominent new species are the weakly bound ultralong-range diatomic molecules composed of a ground state and a Rydberg atom. Theoretically predicted more than a decade ago [10] they have been recently discovered experimentally [11]. The molecular Born-Oppenheimer potential energy surfaces, which are responsible for the diatomic binding, show for these species an unusual strong oscillatory behavior providing a large number of local potential minima.…”

Ultralong-Range Rydberg Cs2 Molecules Investigated at the Ab Initio Level of Theory

“…[4]. This is because the Rydberg electron density becomes more delocalized as the principle quantum number n becomes larger.…”

“…Later on experimental verification of the A*+B type of Rydberg molecules [14,23] has been reported. In 2009 both types of Rydberg molecules have been reported to be directly observed experimentally [4,5]. In Ref.…”

“…Owing to the rapid development on ultracold atoms and molecules [1][2][3], a novel type of molecules, Rydberg molecules become accessible to nowadays experiments [4,5]. A Rydberg molecule is typically formed by the unusually long-range interaction between a Rydberg atom and a ground state (or another Rydberg) atom.…”

“…In Ref. [4] Bendkowsky and coworkers have reported the measured spectra of Rydberg molecular states formed by Rb(5s) and Rb(ns) with high principle quantum number n = 34, · · · , 40. While in Ref.…”