Timothy Barnum

Direct single-shot observation of millimeter-wave superradiance in Rydberg-Rydberg transitions

We have directly detected millimeter wave (mm-wave) free space superradiant emission from Rydberg states (

Coherent laser-millimeter-wave interactions en route to coherent population transfer

n \sim 30

CPMMW SPECTROSCOPY OF RYDBERG STATES OF NITRIC OXIDE

) of barium atoms in a single shot. We trigger the cooperative effects with a weak initial pulse and detect with single-shot sensitivity and 20 ps time resolution, which allows measurement and shot-by-shot analysis of the distribution of decay rates, time delays, and time-dependent frequency shifts. Cooperative line shifts and decay rates are observed that exceed values that would correspond to the Doppler width of 250 kHz by a factor of 20 and the spontaneous emission rate of 50 Hz by a factor of

LASER-MILLIMETER-WAVE TWO-PHOTON RABI OSCILLATIONS EN ROUTE TO COHERENT POPULATION TRANSFER

10^5

ATOMIC PROPERTIES FROM ELECTRONIC STRUCTURE: X 1Σ+ CaF+

. The initial superradiant output pulse is followed by evolution of the radiation-coupled many-body system toward complex long-lasting emission modes. A comparison to a mean-field theory is presented which reproduces the quantitative time-domain results, but fails to account for either the frequency-domain observations or the long-lived features.

Single-shot high-resolution heterodyne detection of millimeter wave superradiance in Rydberg-Rydberg transitions

We demonstrate coherent two-photon population transfer to Rydberg states of barium atoms using a combination of a pulsed dye laser and a chirped-pulse millimeter-wave spectrometer. Numerical calculations, using a density matrix formalism, reproduce our experimental results and explain the factors responsible for the observed fractional population transferred, optimal experimental conditions, and possibilities for future improvements. The long coherence times associated with the millimeter-wave radiation aid in creating coherence between the ground state and Rydberg states, but higher-coherence laser sources are required to achieve stimulated Raman adiabatic passage and for applications to molecules.

IT IS ALL ABOUT PHASE AND IT IS NOT STAR TREK

The spectroscopy of Rydberg states of NO has a long history [1], stimulating both experimental and theoretical advances in our understanding of Rydberg structure and dynamics. The closed-shell ion-core (Σ) and small NO dipole moment result in regular patterns of Rydberg series in the Hund’s case (d) limit, which are well-described by long-range electrostatic models (e.g., [2]). We will present preliminary data on the core-nonpenetrating Rydberg states of NO (orbital angular momentum, ` ≥ 3) collected by chirped-pulse millimeter-wave (CPmmW) spectroscopy. Our technique directly detects electronic free induction decay (FID) between Rydberg states with ∆n* ≈ 1 in the region of n* ∼ 40-50, providing a large quantity (12 GHz bandwidth in a single shot) of high quality (resolution ∼ 350 kHz) spectra. Transitions between high-`, core-nonpenetrating Rydberg states act as reporters on the subtle details of the ion-core electric structure.