Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session J3: Focus Session: Rydberg Atoms and Molecules |
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Chair: Robert Jones, University of Virginia Room: Keller Building 104 |
Thursday, May 29, 2008 11:00AM - 11:36AM |
J3.00001: One-dimensional Rydberg gas in a Magneto-Electric Trap Invited Speaker: We investigate the possibility to trap and align ultracold Rydberg atoms in the regime where both the (coupled) center of mass and electronic motion of the Rydberg atom are of quantum nature. First we explore the properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap being commonly used in ultracold atomic physics experiments. A computational scheme projecting on a single n-manifold and incorporating an adiabatic separation of the electronic and ultracold center of mass motion is developed. An analysis of the resulting adiabatic potential energy surfaces for the center of mass motion demonstrates the possibility of trapping for a class of large angular momentum electronic states. In a second step we study the quantum properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap which is superimposed by a homogeneous electric field. Trapped Rydberg atoms can be created here in long-lived electronic states exhibiting a permanent electric dipole moment of several hundred Debye. The resulting dipole-dipole interaction in conjunction with the radial confinement is demonstrated to give rise to an effectively one-dimensional ultracold quantum Rydberg gas with a macroscopic interparticle distance. We derive analytical expressions for the electric dipole moment and the required linear density of Rydberg atoms. {\bf{ References:}} I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. {\bf{95}}, 053001 (2005)\\ B. Hezel, I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. {\bf{97}}, 223001 (2006)\\ M. Mayle, B. Hezel, I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. {\bf{99}}, 113005 (2007) [Preview Abstract] |
Thursday, May 29, 2008 11:36AM - 11:48AM |
J3.00002: High-gradient Magnetic Guide for Rydberg Atoms R. Mhaskar, C. Hempel, M. Traxler, V. Vaidya, G. Raithel The theory of guided Rydberg atoms and one-dimensional systems of Rydberg atoms has attracted immense interest recently in context of spin chains and one dimensional quantum random walks. Here we describe an experimental setup to guide Rydberg atoms in a high-gradient magnetic trap and provide an outlook toward implementing traps for Rydberg atoms with a very large aspect ratio of 1:1000. The magnetic guide consists of a two-dimensional quadrupole field generated by two parallel wires carrying parallel currents, producing a magnetic-field gradient at the guide center of 2.7~kGauss-cm$^{-1}$. The magnetic guiding of cold, dense beams of $^{87}$Rb atoms is described in [1]. In the guide, the atoms are subjected to a two-step excitation 5S$_{1/2}\rightarrow$5P$_{3/2}\rightarrow$nD$_{5/2}$ process, where $n$ is the principal quantum number of the Rydberg state. For detection, the Rydberg atoms are field-ionized, and the ions are imaged onto a spatially resolving Multi-Channel Plate detector. Due to the high density of the guided atomic beam, the density of the Rydberg atoms is expected to be high, leading to state-mixing collisions. These will populate high angular momentum states having a large magnetic moment and long lifetimes. It is expected that a fraction of the atoms will become trapped and magnetically guided. \textbf{[1]} S. E. Olson, R. R. Mhaskar, and G. Raithel, \emph{Phys. Rev. A} \textbf{73}, 033622 (2006). [Preview Abstract] |
Thursday, May 29, 2008 11:48AM - 12:00PM |
J3.00003: Laser Spectroscopy of Rydberg Atoms in Strong Magnetic Fields B. Knuffman, C. Hempel, R. Mhaskar, E. Paradis, M. Shah, G. Raithel We report on spectroscopy measurements using narrow band laser excitation ($<$ 5 MHz) to probe Rydberg states of laser cooled Rb atoms in high magnetic fields. We report on the energy structure of these states and discuss measuring atomic properties, such as the magnetic dipole moment and other magnetic or electric multipole moments. Additionally, the high energy resolution provided by this spectroscopy technique allows investigations to probe the interactions between Rydberg atoms in high magnetic fields. These are the first high-energy-resolution studies of cold Rydberg atoms in large magnetic fields, where the properties of Rydberg atoms differ significantly from the low-field case. [Preview Abstract] |
Thursday, May 29, 2008 12:00PM - 12:12PM |
J3.00004: High-resolution studies of strongly magnetized, cold Rydberg atoms near the photo-ionization threshold Mudessar Shah, Brenton Knuffman, Eric Paradis, Cornelius Hampel, Rahul Mhaskar, Georg Raithel In previous work, we have studied Rydberg-atom dynamics in the strongly magnetized regime using ultra-cold gases of Rb$^{85}$-atoms prepared in a high-magnetic-field atom trap~[1] Rydberg atoms were excited using a pulsed dye laser with a bandwidth of $\sim~10$~GHz. Interesting features that qualitatively emerged in this previous work included the auto-ionization of individual, metastable quantum states above the photo-ionization threshold and coherent spin oscillations between several magnetic manifolds of the system. Quantitative investigations of these phenomena require a narrow-band excitation scheme. Here, we report on first high-resolution spectroscopic studies of individual quantum states of trapped, strongly magnetized atoms above the photo-ionization threshold using a narrow-band excitation laser ($<~5$MHz linewidth). ``Time dependence and Landau quantization in the ionization of cold, magnetized Ryberg atoms,'' J.-H. Choi, J. R. Guest, E. Hansis, A. P. Povilus, and G. Raithel, Phys. Rev. Lett. {\bf 95}, 253005 (2005). [Preview Abstract] |
Thursday, May 29, 2008 12:12PM - 12:48PM |
J3.00005: Coherent Population Transfer in Rydberg Atoms by Multiphoton Adiabatic Rapid Passage Invited Speaker: It is possible to transfer Rydberg population through up to ten n states by adiabatic rapid passage through a sequence of n to n+1 or n to n-1 transitions using a swept frequency microwave field. However, the microwave frequency sweep must match the changing Kepler frequency. The same population transfer can be effected by a single adiabatic rapid passage through one multiphoton resonance with a much smaller frequency sweep but higher microwave power. The center frequency and power of the microwave pulse are adjusted to select the desired multiphoton transition. The requirements and relative advantages of a multiphoton transition and a sequence of single photon transitions will be discussed. It is a pleasure to acknowledge the contributions of H. Maeda, J. H. Gurian, and D. V. L. Norum to this work. [Preview Abstract] |
Thursday, May 29, 2008 12:48PM - 1:00PM |
J3.00006: One to five photon microwave ionization of Li Rydberg atoms Joshua Gurian, Haruka Maeda, Thomas Gallagher Microwave ionization is a way of connecting field ionization and photoionization. For low n Li Rydberg states the applied microwave frequency is much less than the Kepler frequency. In this well studied regime, microwave ionization occurs by field ionization. In fact, all regimes except the opposite extreme, the microwave photoionization limit, have been studied. Here we report the first measurements of the one to five-photon ionization of Li Rydberg atoms by 17.85 GHz fields. We observe clear steps in the ionization rate as a function of binding energy, so that we can easily see the differences between the one to five photon ionization rates. Somewhat surprisingly, they are not very different. Analysis of the final states of the atoms not ionized by the microwaves shows that population is concentrated in very high n states. This work has been supported by the National Science Foundation. [Preview Abstract] |
Thursday, May 29, 2008 1:00PM - 1:12PM |
J3.00007: Multiphoton adiabatic population transfer in Rydberg atoms: Classical versus Quantum picture Turker Topcu, Francis Robicheaux Coherent population transfer in Rydberg atoms by multiphoton Adiabatic Rapid Passage (ARP) has recently been experimentally realized by Maeda {\it et al} [prl {\bf 96}, 073002 (2006)]. In this process, only one single multiphoton transition is required to coherently transfer population, as opposed to many concurrent single photon transitions. We present results of our classical and fully three dimensional quantum mechanical simulations for efficient multiphoton population transfer in a highly excited Li atom between several pairs of high $n$- manifolds via chirped microwave pulses. We were able to achieve as much as $\sim 70\%$ population transfer from 72p $\rightarrow$ 80p state through a single 8 photon transition. We also discuss the $(n,l)$-distribution of the transferred population, and compare the results from our quantum and classical simulations. We have found that population transfer through multiphoton transitions are classically suppressed compared to the quantum mechanical case and do not require chirping of the microwave pulse. We have also studied the classical phase space for this system in action-angle variables, and found that the physics behind the population transfer can be explained in terms of a hopping scheme over the islands of stability, by mixing into the chaotic sea. [Preview Abstract] |
Thursday, May 29, 2008 1:12PM - 1:24PM |
J3.00008: Microwave Spectroscopy of High-L n=10 Rydberg Levels of Argon Mark E. Hanni, Julie A. Keele, S.R. Lundeen, W.G. Sturrus Using the RESIS/microwave method [1], we have determined the relative positions of the twenty fine structure levels with L $\ge $ 5 in the n=10 Rydberg manifold bound to the $^{2}$P$_{3/2}$ ground state of the Ar$^{+}$ ion. The typical measurement precision ($\pm $0.03 MHz) is approximately a factor of 1000 better than a recent study of similar levels by optical spectroscopy [2]. By comparing the measurements to the predictions of the long-range polarization model, several properties of the Ar$^{+}$ ion can be determined, including its scalar and tensor dipole polarizabilities, its quadrupole moment, and its g-factor. Also determined, but with less precision, are its quadrupole polarizability and its vector hyperpolarizability [3]. \newline [1] R.F. Ward, Jr., W.G. Sturrus, and S.R. Lundeen, Phys Rev. A \underline {53}, 113 (1996) \newline [2] L.E. Wright, E.L. Snow, S.R. Lundeen, and W.G. Sturrus, Phys. Rev. A \underline {75}, 022503 (2007) \newline [3] W. Clark, C.H. Greene, and G. Miecznik, Phys. Rev. A \underline {53}, 2248 (1996) [Preview Abstract] |
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