Exploiting Rydberg blockade to probe strongly-coupled Rydberg atom pairs

Rydberg blockade at very-high- n , n ∼ 300, is examined using strontium n 1 F 3 Rydberg atoms excited in a small volume defined by two crossed tightly-focused laser beams. Strong but not complete blockade is observed and discussed with the aid of quantum calculations using a two-active-electron model. Nonetheless, the probability for creating one, and only one, Rydberg atom is large, >0.6, sufficient to enable study of strongly- coupled Rydberg atom pairs.