Observation of Blueshifted Ultralong-Range Cs2 Rydberg Molecules

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, similar to 15-100 Debye, and accessibility of these states via two-photon association. The observed states are in excellent agreement with theory.