A Hamiltonian for the inclusion of spin effects in long-range Rydberg molecules

TL;DR

This paper develops a Hamiltonian framework incorporating spin effects into the modeling of long-range Rydberg molecules, accounting for hyperfine and spin-orbit interactions to improve spectroscopic accuracy.

Contribution

It introduces a Hamiltonian that explicitly includes spin effects, hyperfine, and spin-orbit interactions in the potential energy calculations of Rydberg molecules.

Findings

Potential energy curves including spin effects are computed for Rb₂ and Cs₂.

Spin degrees of freedom significantly influence molecular multipole moments.

The model aligns with recent experimental observations and advances theoretical understanding.

Abstract

The interaction between a Rydberg electron and a neutral atom situated inside its extended orbit is described via contact interactions for each atom-electron scattering channel. In ultracold environments, these interactions lead to ultra-long-range molecular states with binding energies typically ranging from $10$-$10^4$MHz. These energies are comparable to the relativistic and hyperfine structure of the separate atomic components. Studies of molecular formation aiming to reproduce observations with spectroscopic accuracy must therefore include the hyperfine splitting of the neutral atom and the spin-orbit splittings of both the Rydberg atom and the electron-atom interaction. Adiabatic potential energy curves that fully include these additional effects are presented for Rb$_2$ and Cs$_2$. The influence of spin degrees of freedom on the potential energy curves and molecular multipole moments probed in recent experimental work is elucidated and contrasted with other recent theoretical effort in this direction.