HQOC/ITAMP Joint Quantum Sciences Seminar Wednesday, October 14 , 2015 4:00 PM, Jefferson 250 Prof. Tom Killian, Rice University Ultralong-range Molecules and Autler-Townes Spectroscopy in Strontium Ultracold Rydberg Gases Alkaline-earth metal atoms are attracting increased attention for studies of ultracold Rydberg gases because of new opportunities created by strong core transitions accessible with visible light and the presence of excited triplet states. Core transitions can be used for flexible optical trapping and optical imaging of Rydberg atoms, and triplet levels appear promising for creating stronger optical coupling of ground and Rydberg levels with reduced light scattering. Compared to an alkali metal atom, the existence of both singlet and triplet Rydberg levels creates additional choices of configurations of excited states and associated Rydberg-Rydberg interactions. We have created and characterized ultralong-range Sr2 molecules formed from one ground-state 5s2 1S0 atom and one atom in a 5sns 3S1 Rydberg state for n ranging between 29 and 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation, near resonance with the 5s5p 3P1 intermediate state. Recent measurements of the lifetimes of Rydberg atoms and molecules in dense gases of ground state atoms indicate longer lifetimes for strontium compared to rubidium. We have also studied Autler-Townes spectra in the 5s2 1S0-5s5p 3P1-5sns 3S1 ladder system. Well-resolved doublets are visible in the atom-loss signal when a strong 320 nm pump laser on resonance with the 5s5p3P1-5sns 3S1 transition and a weak 689 nm probe laser near resonance with the 5s2 1S0-5s5p 3P1 are applied. This coherent spectroscopy is very sensitive to Rydberg-Rydberg interactions and reveals effects of underlying spatial correlations between atoms from the Rydberg blockade. Atom loss also shows signatures of an optical bistability. Student Presentation from 4:00-4:10 PM Refreshments Served from 4:10-4:30 PM Guest Presentation from 4:30-6:00 PM -- Clare Ploucha Faculty Assistant to Professors Lukin & Greiner and their labs Department of Physics 17 Oxford St., Lyman 324A Cambridge, MA 02138 P. (617) 496-2544