Bulletin of the American Physical Society
2005 36th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 17–21, 2005; Lincoln, Nebraska
Session G4: Rydberg and Exotic Atoms and Molecules |
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Chair: Jin Wang, University of Nebraska Room: Burnham Yates Conference Center Hawthorne |
Thursday, May 19, 2005 1:30PM - 1:42PM |
G4.00001: Microwave Spectroscopy of High-L, n=10 Rydberg states of Silicon R.A. Komara, E.L. Snow, M.A. Gearba, S.R. Lundeen, C.W. Fehrenbach Using the RESIS/microwave technique [1], we have measured two fine structure intervals between high-L, n=10 Rydberg states of Silicon. A fast Si beam was obtained from an 8 keV Si$^{+}$ beam by charge exchange in an n=10 Rb Rydberg target. Individual n=10 Rydberg levels with L=6-9 were selectively detected by upwards excitation to n=31, using a Doppler tuned CO$_{2}$ laser, followed by Stark ionization of the n=31 level and collection of the resulting ions. This L-selective detection was then used to detect microwave-induced transitions from L=7 to L=8 and from L=8 to =9. The measured intervals give a much improved determination of the dipole polarizability of the ground state of Si$^{+}$,$^{ }$(3p $^{2} $P$_{1/2})$. An unexpected observation is the large ``spin-splitting" between the two levels formed by coupling J$_{c}$ to L. The observed splittings are more than an order of magnitude larger than expected from magnetic interactions. [1] R.A. Komara, M.A. Gearba, C.W. Fehrenback and S.R. Lundeen, J. Phys. B: At. Mol. Opt. Phys. \textbf{38} S87 (2005). [Preview Abstract] |
Thursday, May 19, 2005 1:42PM - 1:54PM |
G4.00002: Fine structure measurements in high-L, n=17 and 20 Rydberg states of barium: A re-determination of the dipole and quadrupole polarizabilities of Ba$^{+}$ E.L. Snow, S.R. Lundeen Two previous studies of Rydberg fine structure in barium have determined the dipole and quadrupole polarizabilities of Ba$^{+ }$[1,2]. The measured dipole polarizability appears to be in good agreement with theoretical calculations, but the quadrupole polarizability and the contribution to it from the single lowest D state are in very poor agreement with the most precise calculations [2]. In an effort to resolve this apparent discrepancy, microwave measurements of higher L fine structure intervals were conducted. RESIS microwave techniques [3,4] have been used to directly measure the fine structure intervals between several n=17 and 20 high-L states. It is hoped that the increased precision of these measurements and the access to higher L levels will clarify the comparison with theory. [1] T.F. Gallagher, R. Kachru, and N.H. Tran, Phys. Rev. A \textbf{26}, 2611 (1982) [2] E.L. Snow, M.A. Gearba, R.A. Komara, and S.R. Lundeen, (to be published) Phys. Rev. A (2005) [3] P.W. Arcuni, E.A. Hessels, and S.R. Lundeen, Phys. Rev. A \textbf{41}, 3648 (1990). [4] R.A. Komara, M.A. Gearba, C.W. Fehrenback and S.R. Lundeen, J. Phys. B: At. Mol. Opt. Phys. \textbf{38} S87 (2005). [Preview Abstract] |
Thursday, May 19, 2005 1:54PM - 2:06PM |
G4.00003: Magnetic trapping of high-angular-momentum Rydberg atoms in strong magnetic fields J.-H. Choi, J. R. Guest, A. P. Povilus, E. Hansis, G. Raithel We report on both the generation and magnetic trapping of high-angular-momentum Rydberg atoms in strong magnetic fields. Clouds of $^{85}$Rb atoms are laser-cooled and trapped in a high-magnetic-field optical molasses and magnetic trap with bias fields of a few Tesla. Long-lived drift-state Rydberg atoms are generated via laser excitation into Rydberg states followed by electron-Rydberg-atom collisions and other collisions in the Rydberg atom gas. Electric-field-ionization detection indicates the presence of long-lived, trapped drift-state Rydberg atoms at delay times of up to 200 ms after the initial excitation. We have studied the dynamics of the trapped Rydberg atoms, and observed initial transient sloshing-type and breathing-mode oscillations. The trapped Rydberg-atom cloud gradually expands, probably due to heating caused by Rydberg-atom collisions. [Preview Abstract] |
Thursday, May 19, 2005 2:06PM - 2:18PM |
G4.00004: Emission of fast Rydberg atoms from cold Rydberg-atom gases Brenton Knuffman, Georg Raithel Rydberg-Rydberg collisions in a cold, dense Rydberg gas may lead to the conversion of internal energy into center-of-mass energy of the colliding atoms, resulting in Rydberg-atom velocities much larger than the initial velocities in the gas. We prepare cold Rydberg-atom gases by laser excitation of laser-cooled atom clouds, and use time-of-flight measurements to demonstrate the production of fast Rydberg atoms. The velocity distributions of Rydberg atoms emerging from the Rydberg-atom gases are obtained. State-selective field ionization spectra indicate a correspondence of fast Rydberg atoms with strong l-mixing and Penning ionization signals, which are characteristic of collisions between Rydberg atoms. The production of fast Rydberg atoms exhibits a strong dependence on the density of the atomic sample. The dependence on the initial principal quantum state of the Rydberg atoms is also discussed. [Preview Abstract] |
Thursday, May 19, 2005 2:18PM - 2:30PM |
G4.00005: Coherent Population Transfer of Ground State Atoms into Rydberg States Aaron Reinhard, Tara Cubel, Kevin Teo, Vladimir Malinovsky, Jeff Guest, Brenton Knuffman, Paul Berman, Georg Raithel Using the STIRAP technique, we have excited laser-cooled rubidium atoms from the $5S_{1/2}$ ground state into the $44D_ {5/2}$ Rydberg state with an efficiency of up to $\sim$ 70\%. Two consecutive STIRAP sequences are applied to the same atom sample, allowing us to extract the excitation efficiency from the ratio of Rydberg atom counts detected after the two sequences. Experimental results are compared with the results of density-matrix calculations, and good agreement is found. Using STIRAP excitation, we have observed spectral broadening of resonance lines of 60-80MHz when exciting to the higher-lying 84D Rydberg state. Using samples of just a few tens of atoms, we have measured probability distributions for the number of Rydberg atoms excited in a single pulse. For resonant excitation, the distributions exhibit a sub-Poissonian character (Q=0.8-0.9), indicating the presence of a blockade effect due to Van-der-Waals interactions. [Preview Abstract] |
Thursday, May 19, 2005 2:30PM - 2:42PM |
G4.00006: Simulations of Rydberg-Rydberg Interactions Francis Robicheaux, Jesus Hernandez We present the results of simulations of strongly interacting Rydberg atoms. We have investigated the interaction between two Rydberg atoms and have performed approximate calculations of the interaction between many Rydberg atoms. The focus of the talk will be on simulations of many body effects in a Rydberg gas. In particular, we will examine correlation effects: the dependence of the state of atom A on the state of atom B. Through a judicious choice of basis function we are able to directly simulate the quantum state for more than 20 atoms. [Preview Abstract] |
Thursday, May 19, 2005 2:42PM - 2:54PM |
G4.00007: Many-Body Interactions in a Restricted Dimensionality Sample of Ultra-cold Rydberg Atoms Thomas J. Carroll, Shubha Sunder, Michael W. Noel Ultra-cold 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 a long, thin column of atoms in the MOT to Rydberg states. At low density, where the sample is nearly one-dimensional, many-body interactions are suppressed. At higher densities the sample becomes three-dimensional and many-body effects are apparent. This work was supported by the National Science Foundation under Grant No. 0134676. [Preview Abstract] |
Thursday, May 19, 2005 2:54PM - 3:06PM |
G4.00008: Is a multi walled nanotube one-dimensional? Mikhail Zamkov, Nathan Woody, Bing Shan, Zenghu Chang, Patrick Richard Despite the structural similarity between the single and multi walled nanotubes (SWNTs and MWNTs), the nature of electron transport in these systems was found to be fundamentally different. In contrast to a SWNT, where conduction electrons are constrained to interact in a strictly one--dimensional manner (Luttinger-liquid system), electron excitations in a MWNT exhibit a distinct multi--dimensional Fermi--liquid behavior. The latter was demonstrated experimentally by comparing the femtosecond decay dynamics of electrons excited into different conduction bands of a MWNT, consisting, on average, of 15 coaxial SWNT shells. The observed temporal evolution provides strong evidence that long--range e--e interaction along the tube vanishes due to screening, indicating that multi-- dimensional nature of charge propagation should be invoked in modeling electronic properties of MWNTs. This work was supported by Chemical Sciences, Geo--sciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy. [Preview Abstract] |
Thursday, May 19, 2005 3:06PM - 3:18PM |
G4.00009: Threshold behavior of bosonic two-dimensional few-body systems Doerte Blume Bosonic two-dimensional self-bound clusters consisting of N atoms interacting through additive van der Waals potentials become unbound at a critical mass m*(N); m*(N) has been predicted to be independent of the size of the system. Furthermore, it has been predicted that the binding energy E(N) of the N-atom system varies exponentially as the atomic mass approaches m*. We report accurate numerical many-body calculations that allow these predictions to be tested. We confirm the existence of a universal critical mass m* and show that the near-threshold behavior can only be described properly if a previously neglected term is included. We also comment on the universality of the energy ratio E(N+1)/E(N) near threshold. *This work is supported by the NSF and the PRF. [Preview Abstract] |
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