We observe ultralong-range blue-shifted Cs2 molecular states in an optical dipole trap. The accidental near degeneracy of (n-4)l and ns Rydberg states for l>2 leads to non-adiabatic coupling, producing potential wells above the ns thresholds.
We observe ultralong-range blueshifted Cs(2) molecular states near ns(1/2) Rydberg states in an optical dipole trap, where 31≤n≤34. The accidental near degeneracy of (n-4)l and ns Rydberg states for l>2 in Cs, due to the small fractional ns quantum defect, leads to nonadiabatic coupling among these states, producing potential wells above the ns thresholds. Two important consequences of admixing high angular momentum states with ns states are the formation of large permanent dipole moments, ~15-100 Debye, and accessibility of these states via two-photon association. The observed states are in excellent agreement with theory.
Vibrational properties of ultralong Rydberg Cs2 molecules are investigated on corresponding potential curves obtained by perturbation theory. The Rydberg Cs2 molecules are associated by a Rydberg Cs(nS/nP) atom (n=30−70) and a ground state Cs(6s) atom. The starting point for the perturbation treatment of corresponding Rydberg molecular potential curves is to generate accurate atomic Rydberg states from realistic {\it ab initio} effective core potential. The calculated results have similar characteristics with available experimental and theoretical investigations on Rydberg Rb2 molecules. And this is the first time that Rydberg molecules are studied at the {\it ab initio} level.
We consider ultralong-range polyatomic Rydberg molecules formed by combining a Rydberg cesium atom and a ground-state RbCs molecule. We explore the regime where the charge-dipole interaction due to the Rydberg electron with the diatomic polar molecule couples the quantum defect Rydberg states Cs(ns) to the nearest degenerate hydrogenic manifold. We consider polyatomic Rydberg molecules in states which are amenable to production in optical tweezers and study the influence of nonadiabatic coupling on the likelihood of their formation. The decay rates of the vibrational states reflect the interference signature of wave function spread in different coupled potential wells.
Observation of Blueshifted Ultralong-Range Cs2 Rydberg Molecules
Ultralong-range Rydberg molecules provide an exciting testbed for molecular physics at exaggerated scales. In the so-called trilobite and butterfly Rydberg molecules, the Born-Oppenheimer approximation can fail due to strong nonadiabatic couplings arising from the combination of radial oscillations and rapid energy variations in the adiabatic potential energy curves. We utilize an accurate coupled-channel treatment of the vibronic system to observe the breakdown of Born-Oppenheimer physics, such as nonadiabatic trapping and decay of molecular states found near pronounced avoided crossings in the adiabatic potential curves. Even for vibrational states localized far away from avoided crossings, a single-channel model is quantitatively sufficient only after including the diagonal nonadiabatic corrections to the Born-Oppenheimer potentials. Our results indicate the importance of including nonadiabatic physics in the description of ultralong-range Rydberg molecules and in the interpretation of measured vibronic spectra.