Microwave multiphoton transitions between Rydberg states driven by chirped pulses

Matthew Doogue, Julia H. Rentz, C. W. S. Conover

Yong Li, Jianguo Rao, Baiwen Li

J. H. Gurian

C. W. S. Conover, Matthew P. Doogue, Friedrich Struwe

Rydberg atoms in a static electric field provide an experimental system with which many aspects of strong atom-field interactions can be tested. We report measurements of multiphoton transitions in Rydberg states of potassium driven by chirped pulses of rf radiation. Pulses of rf are produced with frequencies swept from 675 to 825 MHz at rates from 0.25 MHz/ns to 7.5 MHz/ns. We present measurements of population transfer in a two-level system as a function of rf field strength and sweep rate. The data is analyzed with a dynamical Floquet model using Landau-Zener transition probabilities; this model accurately describes these transitions.

Türker Topçu, F. Robicheaux

Following an experimental observation, a recent simulation has shown that efficient population transfer can be achieved through adiabatic chirping of a microwave pulse through a 10-photon resonance connecting two Rydberg states with n = 72, ℓ = 1 and n ∼ 82. These simulations have revealed that this population transfer is essentially a classical transition caused by separatrix crossing in the classical phase space. Here, we present the results of our fully three-dimensional quantum and classical simulations of coherent multiphoton population transfer in a kicked Li atom in a Rydberg state. We were able to achieve ∼76% population transfer from the 40p to 46p state in Li through a 6-photon resonance and contrast our results with those when the transition is driven by microwaves. We further discuss the case when the atom starts out from a Stark state in conjunction with the ℓ-distribution of the transferred population. We use a one-dimensional classical model to investigate the classical processes taking place in the phase space and find that the same separatrix crossing mechanism observed in microwave transitions is also responsible for the transition when the atom is kicked.

Thomas F. Gallagher

Microwave ionization and excitation of Rydberg atoms provides a system in which quantitative experiments can be done to study single electron atoms in strong fields. In many cases microwave ionization proceeds by means of transitions through other bound states. Multiphoton transitions between two relatively isolated K Rydberg states have been examined under a variety of circumstances to establish the connection between transitions driven by quasi static fields and photon absorption and to understand the evolution during pulses of microwaves.