Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts

TL;DR

This paper investigates large Zeeman shifts in ultracold Sr2 molecules, revealing nonadiabatic effects and testing advanced theoretical models through precise measurements of molecular energy shifts.

Contribution

It demonstrates how nonadiabatic couplings cause anomalous Zeeman shifts and uses these effects to validate high-precision ab initio molecular models.

Findings

Large linear and quadratic Zeeman shifts observed

Nonadiabatic effects explained by Coriolis coupling

Quadratic shifts test advanced ab initio models

Abstract

Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold $^{88}$Sr$_2$ molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite $f$-parity states and exhibit fourth-order corrections, providing a stringent test of a state-of-the-art \textit{ab initio} model.