Observation of Quantum Beating in Rubidium at 2

Observation of Quantum Beating in Rubidium at 2. 1 THz and 18. 2 THz: Long-Range Rb*-Rb Interactions. WILLIAM GOLDSHLAG, BRIAN J. RICCONI, J. GARY EDEN Laboratory for Optical Physics and Engineering, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA. 2017 -06 -20 1

Overview • Quantum beating has been observed at frequencies up to 55 THz. • Interaction between 7 s-5 d and 8 s-6 d wave packets is observed. • A new tool for probing Rb*-Rb* interactions at long range (100 -1000Å). 2

Quantum Beat Spectroscopy 3

Excitation of Atomic Wave Packets in Rubidium Spectrum of coherent excitation source 7 s 5 d 4

Schematic Diagram of the Experimental Layout 55 fs Ti: Al 2 O 3 laser ΔT dichroic mirror Quantum beating intensity 50/50 Oven Laser pump power Delay stage Beam profiler 5

Quantum Beating in Time Domain 6

Strong Quantum Beats in Time Domain Energy levels of Rb producing strongest quantum beating 7

Spectral Intensity of 6 p Emission to Ground (420 nm) 8

Spectral Lines Attributed to Wave Packet Interactions 9

Optical Process Generating the 18. 225 THz Quantum Beating 10

Optical Process Generating the 2. 107 THz Quantum Beating 11

Optical Process Generating the 10. 73 THz Quantum Beating 12

Spectral Lines Attributed to Wave Packet Interactions 13

Perspective View of a Spectrogram 14

Perspective View of a Spectrogram 15

Temporal Behavior of Main Quantum Beating Lines Plots are not to scale. “ 5 s-p-d” 7 s-5 d 8 s-6 d Energy levels of Rb comprising the wave packets. Time delay between pulses, ps. 16

Temporal Behavior of Main Quantum Beating Lines Plots are not to scale. 7 s-5 d 2 x (7 s-5 d) Energy levels of Rb comprising the wave packets. Time delay between pulses, ps. 17

Summary Observed quantum beating in rubidium at frequencies up to 55 THz using parametric four-wave mixing. Multiple wave packets were simultaneously observed, and they appear to be trading energy. The wave packets allow us to look into long-range interactions of rubidium atoms, making quantum beat spectroscopy a new tool for studying molecular interactions. 18