2016/07/14 by Heiner Saßmannshausen, Saßmannshausen, Heiner, Johannes Deiglmayr +3
Physics and Astronomy · Chemistry · #Cold Atom Physics and Bose-Einstein Condensates #Spectroscopy and Laser Applications #Quantum, superfluid, helium dynamics
paper · pdf · doi:10.48550/arxiv.1607.04060
We present an overview of our recent investigations of long-range\ninteractions in an ultracold Cs Rydberg gas. These interactions are studied by\nhigh-resolution photoassociation spectroscopy, using excitation close to\none-photon transitions into np3/2 Rydberg states with pulsed and\ncontinuous-wave ultraviolet laser radiation, and lead to the formation of\nlong-range Cs2 molecules. We observe two types of molecular resonances. The\nfirst type originates from the correlated excitation of two atoms into\nRydberg-atom-pair states interacting at long range via multipole-multipole\ninteractions. The second type results from the interaction of one atom excited\nto a Rydberg state with one atom in the electronic ground state. Which type of\nresonances is observed in the experiments depends on the laser intensity and\nfrequency and on the pulse sequences used to prepare the Rydberg states. We\nobtain insights into both types of molecular resonances by modelling the\ninteraction potentials, using a multipole expansion of the long-range\ninteraction for the first type of resonances and a Fermi-contact\npseudo-potential for the second type of resonances. We analyse the relation of\nthese long-range molecular resonances to molecular Rydberg states and ion-pair\nstates, and discuss their decay channels into atomic and molecular ions. In\nexperiments carried out with a two-colour two-photon excitation scheme, we\nobserve a large enhancement of Rydberg-excitation probability, which we\ninterpret as a saturable autocatalytic antiblockade phenomenon.\n