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Articles 1 - 13 of 13
Full-Text Articles in Physics
Quantum Control Via A Genetic Algorithm Of The Field Ionization Pathway Of A Rydberg Electron, Vincent C. Gregoric, Xinyue Kang, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel
Quantum Control Via A Genetic Algorithm Of The Field Ionization Pathway Of A Rydberg Electron, Vincent C. Gregoric, Xinyue Kang, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel
Physics and Astronomy Faculty Publications
Quantum control of the pathway along which a Rydberg electron field ionizes is experimentally and computationally demonstrated. Selective field ionization is typically done with a slowly rising electric field pulse. The (1/n*)4 scaling of the classical ionization threshold leads to a rough mapping between arrival time of the electron signal and principal quantum number of the Rydberg electron. This is complicated by the many avoided level crossings that the electron must traverse on the way to ionization, which in general leads to broadening of the time-resolved field ionization signal. In order to control the ionization pathway, thus …
Imaging The Dipole-Dipole Energy Exchange Between Ultracold Rubidium Rydberg Atoms, Donald P. Fahey, Thomas J. Carroll, Michael W. Noel
Imaging The Dipole-Dipole Energy Exchange Between Ultracold Rubidium Rydberg Atoms, Donald P. Fahey, Thomas J. Carroll, Michael W. Noel
Physics and Astronomy Faculty Publications
The long-range, anisotropic nature of the interaction among atoms in an ultracold dipolar gas leads to a rich array of possibilities for studying many-body physics. In this work, an ultracold gas of highly excited atoms is used to study energy transport due to the long-range dipole-dipole interaction. A technique is developed to measure both the internal energy states of the interacting Rydberg atoms and their positions in space. This technique is demonstrated by observing energy exchange between two spatially separated groups of Rydberg atoms excited to two different internal states. Simulations confirm the general features of the energy transport in …
Experimental Investigation Of Long-Lived Rydberg States In Ultracold Argon, G. Ranjit, C. I. Sukenik
Experimental Investigation Of Long-Lived Rydberg States In Ultracold Argon, G. Ranjit, C. I. Sukenik
Physics Faculty Publications
We report on our investigation of the formation and survival of long-lived Rydberg states in argon produced by pulsed laser excitation of ultracold metastable state argon atoms in a magneto-optical trap. The states studied have a 2P1/2 core. Low angular momentum Rydberg states with this core normally autoionize rapidly. If, however, atoms are excited in the presence of electric fields, higher angular momentum states, traditionally termed ZEKE states (ZEKE is derived from zero kinetic energy) can be formed. The lifetime of these states can be orders of magnitude greater than low angular momentum states. In this paper, we report on …
Simulations Of The Dipole-Dipole Interaction Between Two Spatially Separated Groups Of Rydberg Atoms, Thomas J. Carroll, Christopher Daniel, Leah Hoover, Timothy Sidie, Michael Noel
Simulations Of The Dipole-Dipole Interaction Between Two Spatially Separated Groups Of Rydberg Atoms, Thomas J. Carroll, Christopher Daniel, Leah Hoover, Timothy Sidie, Michael Noel
Physics Faculty Research and Scholarship
The dipole-dipole interaction among ultracold Rydberg atoms is simulated. We examine a general interaction scheme in which two atoms excited to the x and x(') states are converted to y and y(') states via a Förster resonance. The atoms are arranged in two spatially separated groups, each consisting of only one species of atom. We monitor the state mixing by recording the fraction of atoms excited to the y(') state as the distance between the two groups is varied. With zero detuning a many-body effect that relies on always resonant interactions causes the state mixing to have a finite range. …
Recombination Fluorescence In Ultracold Neutral Plasmas, Scott D. Bergeson, F. Robicheaux
Recombination Fluorescence In Ultracold Neutral Plasmas, Scott D. Bergeson, F. Robicheaux
Faculty Publications
We present the first measurements and simulations of recombination fluorescence from ultracold neutral calcium plasmas. This method probes three-body recombination at times less than 1 µs, shorter than previously published time scales. For the lowest initial electron temperatures, the recombination rate scales with the density as n22, significantly slower than the predicted n3. Recombination fluorescence opens a new diagnostic window in ultracold plasmas. In most cases it probes deeply bound level populations that depend critically on electron energetics. However, a perturbation in the calcium 4snd Rydberg series allows our fluorescence measurements to probe the population in weakly bound levels that …
Many-Body Interactions In A Sample Of Ultracold Rydberg Atoms With Varying Dimensions And Densities, Thomas J. Carroll, Shubha Sunder, Michael W. Noel
Many-Body Interactions In A Sample Of Ultracold Rydberg Atoms With Varying Dimensions And Densities, Thomas J. Carroll, Shubha Sunder, Michael W. Noel
Physics and Astronomy Faculty Publications
Ultracold highly excited atoms in a magneto-optical trap (MOT) are strongly coupled by the dipole-dipole interaction. We have investigated the importance of many-body effects by controlling the dimensionality and density of the excited sample. We excited three different cylindrical volumes of atoms in the MOT to Rydberg states. At small radius, where the sample is nearly one-dimensional, many-body interactions are suppressed. At larger radii, the sample becomes three-dimensional and many-body effects are apparent.
Angular Dependence Of The Dipole-Dipole Interaction In A Nearly One-Dimensional Sample Of Rydberg Atoms, Thomas J. Carroll, Katharine Claringbould, Anne Goodsell, M. J. Lim, Michael W. Noel
Angular Dependence Of The Dipole-Dipole Interaction In A Nearly One-Dimensional Sample Of Rydberg Atoms, Thomas J. Carroll, Katharine Claringbould, Anne Goodsell, M. J. Lim, Michael W. Noel
Physics and Astronomy Faculty Publications
Atoms in an ultracold highly excited sample are strongly coupled through the dipole-dipole interaction. In an effort to understand and manipulate the complicated interactions in this system we are investigating their dependence on the relative orientation of the dipoles. By focusing a 480 nm beam from a tunable dye laser into a magneto-optical trap, we produce a nearly one-dimensional sample of Rydberg atoms. The trap lies at the center of four conducting rods with which we can vary the magnitude and direction of the electric field at the trap, thus controlling the orientation of the dipoles with respect to the …
Fragmentation Processes Following Core Excitation In Acetylene And Ethylene By Partial Ion Yield Spectroscopy, Maria Novella Piancastelli, Wayne C. Stolte, Gunnar Ohrwall, S-W Yu, D. Bull, K. Lantz, Alfred S. Schlachter, Dennis W. Lindle
Fragmentation Processes Following Core Excitation In Acetylene And Ethylene By Partial Ion Yield Spectroscopy, Maria Novella Piancastelli, Wayne C. Stolte, Gunnar Ohrwall, S-W Yu, D. Bull, K. Lantz, Alfred S. Schlachter, Dennis W. Lindle
Chemistry and Biochemistry Faculty Research
Partial ion yield spectroscopy provides a very detailed picture of fragmentation processes following core excitation in isolated molecules. We exploit this potential in the analysis of decay processes following C1s→π and C1s→Rydberg excitations in ethylene and acetylene. We show that the relative intensity of spectral features related to the excitation to empty molecular orbitals or to Rydberg states is a function of the time variation of the fragmentation process. Namely, we see an intensity increase in the Rydberg states compared to the molecular orbitals as the fragmentation process becomes more extensive, a result attributable to the diffuse nature of the …
Electric Field Controlled, Pulsed Autoionization In Two Electron Wave Packets, J. Greg Story, Heider N. Ereifej
Electric Field Controlled, Pulsed Autoionization In Two Electron Wave Packets, J. Greg Story, Heider N. Ereifej
Physics Faculty Research & Creative Works
In this paper, control of the evolution of a two electron wave packet through the application of a static electric field is demonstrated. Specifically, application of a small electric field is used to produce pulsed autoionization events, the timing of which can be controlled on a picosecond time scale. The technique is demonstrated by exciting calcium atoms using a short-pulsed laser to the 4p3/219d doubly excited state, which is energy degenerate with the 4p1/2nk stark states. Evolution of the resultant wave packet is monitored through the application of a second short laser pulse, which stimulates the …
Exact Analytic Relation Between Quantum Defects And Scattering Phases With Applications To Green’S Functions In Quantum Defect Theory, V. E. Chernov, N. L. Manakov, Anthony F. Starace
Exact Analytic Relation Between Quantum Defects And Scattering Phases With Applications To Green’S Functions In Quantum Defect Theory, V. E. Chernov, N. L. Manakov, Anthony F. Starace
Anthony F. Starace Publications
The relation between the quantum defects, μλ, and scattering phases, δλ, in the single-channel Quantum Defect Theory (QDT) is discussed with an emphasis on their analyticity properties for both integer and noninteger values of the orbital angular momentum parameter λ. To derive an accurate relation between μλ and δλ for asymptotically-Coulomb potentials, the QDT is formally developed for the Whittaker equation in its general form “perturbed” by an additional short-range potential. The derived relations demonstrate that μλ is a complex function for above-threshold energies, which is analogous to the fact that δ …
Ionization Of Rydberg Wave Packets By Subpicosecond, Half-Cycle Electromagnetic Pulses, C. Raman, C. W. S. Conover, C. I. Sukenik, P. H. Bucksbaum
Ionization Of Rydberg Wave Packets By Subpicosecond, Half-Cycle Electromagnetic Pulses, C. Raman, C. W. S. Conover, C. I. Sukenik, P. H. Bucksbaum
Physics Faculty Publications
We have studied the ionization of Rydberg wave packets by subpicosecond, nearly unipolar electromagnetic field pulses, in the regime where the duration of the electric field is less than the classical Kepler orbit time 2n3 for the wave packet. In contrast to the subpicosecond optical pulses, subpicosecond field pulses can ionize wave packets when the probability density near the inner turning point of the Kepler orbit is low. The transfer of energy from the electromagnetic field to essentially free electrons demonstrates that the pulses are substantially shorter than one field cycle. Such half-cycle pulses can track the wave packet throughout …
Landau-Zener Treatment Of Intensity-Tuned Multiphoton Resonances Of Potassium, J. Greg Story, D. I. Duncan, Thomas F. Gallagher
Landau-Zener Treatment Of Intensity-Tuned Multiphoton Resonances Of Potassium, J. Greg Story, D. I. Duncan, Thomas F. Gallagher
Physics Faculty Research & Creative Works
When exposed to intense light of ~580 nm, the ground state of K shifts up in energy, passing through two photon resonances with Rydberg states, and finally crossing the two-photon ionization limit. We have used laser pulses of varying duration to study the nature of the population transfer from the ground state to the excited state due to the intensity-tuned resonances encountered during the rising edge of the pulse. A dynamic Floquet approach in which the resonances are treated as avoided crossings of the Floquet energy levels is used to model the population transfer and gives excellent agreement with the …
Size‐Inconsistency Effects In Molecular Properties For States With Valence‐Rydberg Mixing: The Low‐Lying Π→Π∗ States Of Ethylene And Butadiene, Robert J. Cave
Size‐Inconsistency Effects In Molecular Properties For States With Valence‐Rydberg Mixing: The Low‐Lying Π→Π∗ States Of Ethylene And Butadiene, Robert J. Cave
All HMC Faculty Publications and Research
Ab initio results for the low‐lying 1B1u states of ethylene are used to discuss size‐inconsistency effects on calculated molecular properties for states where valence‐Rydberg mixing is important. Results for the expectation value of x2, x being the coordinate perpendicular to the plane of the molecule, are presented from quasidegenerate variational perturbation theory and multireference configuration‐interaction calculations. These results are compared with values from previous studies. It is argued that size inconsistency in configuration‐interaction studies can have a significant effect on estimated molecular properties. Calculations on several low‐lying states of butadiene are also reported where similar size‐inconsistency effects are found.