Chirped-pulse millimeter-wave spectroscopy, dynamics, and manipulation of Rydberg-Rydberg Transitions

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 131-138).The chirped-pulse millimeter-wave (CPmmW) technique is applied to transitions between Rydberg states, and calcium atoms are used as the initial test system. The unique feature of Rydberg{Rydberg transitions is that they have enormous electric dipole transition moments: ~5 kiloDebye at n* ~45, where n* is the eective principal quantum number. After polarization by a mm-wave pulse in the 70{84 GHz frequency region, the excited transitions re-radiate free induction decay (FID) at their resonant frequencies, and the FID is heterodyne-detected by the CPmmW spectrometer. Data collection and averaging are performed in the time domain. The spectral resolution is ~100 kHz. Because of the large transition dipole moments, the available mm-wave power is sucient to polarize the entire bandwidth of the spectrometer (12 GHz) in each pulse, and high-resolution survey spectra may be collected. Both absorptive and emissive transitions are observed, and they are distinguished by the phase of their FID relative to that of the excitation pulse. With the combination of the large transition dipole moments and direct monitoring of transitions, dynamics are observed, such as transient nutations from the interference of the excitation pulse with the polarization that it induces in the sample. Transient nutations also provide information about the sample, such as the dipole moment and the number density of Rydberg states. Since the waveform produced by the mm-wave source may be precisely controlled, states with high angular momentum may be populated by a sequence of pulses while recording the results of these manipulations in the time domain. Also, the superradiant decay of the Rydberg sample is probed both directly through FID and indirectly using photon echoes. Prospects for further manipulations, such as adiabatic rapid passage, composite pulses, and optical/mm-wave stimulated Raman adiabatic passage, are evaluated. The application of the CPmmW technique to transitions between Rydberg states of molecules is discussed.by Anthony P. Colombo.Ph.D

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

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.National Science Foundation (U.S.) (Grant 1122374