Vibrationally highly excited trilobite molecules stabilized by non-adiabatic coupling

TL;DR

This paper reports the first observation of highly excited vibrational states in trilobite ultralong-range Rydberg molecules, demonstrating stabilization via non-adiabatic coupling and opening new avenues for manipulating quantum states in long-range molecules.

Contribution

It provides the first direct measurement of beyond-Born-Oppenheimer effects in long-range Rydberg molecules, highlighting the role of non-adiabatic coupling in stabilizing vibrational states.

Findings

Observation of vibrational states at $ u \,\sim\, 100$ in Rb trilobite molecules.

Stability of these states due to suppression of adiabatic decay pathways.

Identification of specific Rydberg levels where avoided crossings enable diabatic traversal.

Abstract

We report on the observation of highly excited ($\nu \sim 100)$ vibrational states of a trilobite ultralong-range Rydberg molecule in $^{87}$Rb. These states manifest spectroscopically in a regularly spaced series of peaks red-detuned from the $25f_{7/2}$ dissociation threshold. The existence and observed stability of these states requires the almost complete suppression of the adiabatic decay pathway induced by the $P$-wave shape resonance of Rb. This stabilization is predicted to occur only for certain Rydberg levels where the avoided crossing between trilobite and $P$-wave dominated butterfly potential energy curves nearly vanishes, allowing the vibrational states to diabatically traverse the crossing with almost unit probability. This is the first direct measurement of beyond-Born-Oppenheimer physics in long-range Rydberg molecules, and paves the way for future experiments to access and manipulate wavepackets formed from high-lying vibrational states.