Bulletin of the American Physical Society
2006 Ohio Section of the APS Spring Meeting
Friday–Saturday, March 31–April 1 2006; Detroit, Michigan
Session S7: Phenomena and Applications in Atomic Physics |
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Chair: Boris Nadgorny Room: McGregor Center FG |
Saturday, April 1, 2006 9:36AM - 9:48AM |
S7.00001: VCSEL-based CPT atomic clock: Understanding the magic modulation index Michael Crescimanno, Irina Novikova, Yanhong Xiao, David Phillips, Ron Walsworth Since the earliest VCSEL-based CPT experiments [1] it has been known that there are modulation regimes that allow the measured clock frequency to be largely independent of laser intensity. We describe a quantum optics model of the VCSEL-based CPT clock and compare the model to recent experimental lineshape data. This is part of a stringent test of the computation of coupled channel AC stark effects in multiphoton processes. \newline \newline [1] Vanier, J., A. Godone, F. Levi, S. Michalizio, ``Atomic Clocks Based on Coherent Population Trapping: Basic Theoretical Models and Frequency Stability,'' Proceedings of the 2003 IEEE International Frequency Control Symposium, Pg. 2-14. [Preview Abstract] |
Saturday, April 1, 2006 9:48AM - 10:00AM |
S7.00002: Investigations of Positron Annihilation with Atoms and Molecules using PsARS W.E. Kauppila, J.J. Edwards, E.G. Miller, T.S. Stein, E. Surdutovich Positrons, being the antiparticles of electrons, ultimately annihilate either directly with electrons (that are free or attached to atoms or molecules), or via the formation of positronium (Ps, a short-lived atom composed of a positron and an electron) with subsequent annihilation. In this work we have developed positronium annihilation ratio spectroscopy (PsARS), and are using PsARS to investigate the formation and destruction of Ps [1], as well as positron attachment to molecules. For this experiment a 3 to 100 eV positron beam obtained from a sodium-22 radioactive source is passed through a gas scattering cell and resulting annihilation gamma rays of different energies are detected in coincidence. Annihilation measurements, such as these, have astrophysical relevance since characteristic positron annihilation gamma rays have been observed from various extraterrestrial sources (e.g., solar flares and the direction towards the center of our galaxy). [1] W.E. Kauppila, E.G. Miller, H.F.M. Mohamed, K. Pipinos, T.S. Stein and E. Surdutovich, Phys. Rev. Lett. 93, 113401 (2004). [Preview Abstract] |
Saturday, April 1, 2006 10:00AM - 10:12AM |
S7.00003: Ionization Cross Sections for 10-25 keV Proton Impact on Helium J. Kang, G.S. Hodges, J.D. Thomas, T.J. Kvale, D.G. Seely Absolute ionization cross sections are obtained by the energy-loss spectra of helium for proton impact. Experimentally, the incident proton beam with kinetic energies of 10-25 keV was directed through a target cell containing helium gas at room temperature. The scattered proton beam was then energy analyzed to obtain energy-loss spectra. These spectra were then used to obtain absolute, differential (in energy), ionization cross sections. By integrating the differential cross sections, we also obtained absolute total ionization cross sections. [Preview Abstract] |
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