Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session G2: Invited Session: Precision Measurements in Ion Traps |
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Chair: James Thompson, JILA Room: 200B |
Wednesday, June 5, 2013 8:00AM - 8:30AM |
G2.00001: Precision comparison of the g-factor of the proton and anti-proton Invited Speaker: Jack DiSciacca We report the first measurement of the antiproton magnetic moment using a single antiproton. The magnetic moment in nuclear magnetons is $\mu_{\bar{p}}/\mu_N = - 2.792 845 \pm 0.000 012$, a 4.4 parts per million (ppm) measurement. This represents a factor of 680 improvement in precision over previous work using exotic atom spectroscopy, which has achieved a 3000 ppm precision and remained essentially unchanged in the past 20 years.\footnote{A. Kreissl, et al. Z. Phys. C: Part. Fields \textbf{37}, 557 (1988).}$^{,}$\footnote{T. Pask, et al. Phys. Lett. B \textbf{678}, 55 (2009).} Our measurement allows for an improved comparison of the proton and antiproton magnetic moments, yielding a result consistent with the prediction of charge, parity and time reversal symmetry. Following a proof of principle, 2.5 ppm measurement of the proton magnetic moment,\footnote{J. DiSciacca and G. Gabrielse. Phys. Rev. Lett. \textbf{108}, 153001 (2012)} the experiment was moved to CERN for the antiproton experiment. Initial work focused on catching, cooling and trapping a single antiproton from the 5 MeV beam at CERN's Antiproton Decelerator. Following this work, we undertook a magnetic moment measurement. The spin and cyclotron frequency are measured to determine the g-factor, $g/2 = f_s/f_c$. Prospects for further improvement should be possible with single spin flip detection, similar to what was used to measure the electron magnetic moment - currently the most precisely measured property of a fundamental particle.\footnote{D. Hanneke, S. Fogwell, and G. Gabrielse, Phys. Rev. Lett. \textbf{100}, 120801 (2008).} The new antiproton magnetic moment measurement is likely a first step towards improved precision by an additional factor of $10^3$ or $10^4$ improvement, with a precision at the part per billion level.\footnote{N. Guise, J. DiSciacca, and G. Gabrielse. Phys. Rev. Lett. \textbf{104}, 143001 (2009).}$^{,}$\footnote{S. Ulmer, et al. Phys. Rev. Lett. \textbf{106}, 253001 (2011).}$^{,}$\footnote{C. C. Rodegheri, et a.l New J. Phys. \textbf{14}, 063011 (2012).} [Preview Abstract] |
Wednesday, June 5, 2013 8:30AM - 9:00AM |
G2.00002: g-factor measurements of hydrogen-like ions and a new electron mass Invited Speaker: Sven Sturm |
Wednesday, June 5, 2013 9:00AM - 9:30AM |
G2.00003: High-resolution spectroscopy of cold HD$^+$ molecular ions Invited Speaker: Stephan Schiller HD$^+$ is a fundamental quantum system: it is a three-body bound quantum system that can be accurately described ab initio by Quantum Electrodynamics, using as input certain fundamental constants. A comparison between experimental HD$^+$ transition frequencies and the ab initio results therefore provides a test of the validity of theoretical treatments, and/or a determination of these fundamental constants. At present, the experimental inaccuracies of the transition frequency measurements is still higher than the theoretical or fundamental constants inaccuracies, resulting in an on-going experimental challenge. Many applications of cold molecular ions have been proposed. They would benefit strongly from availability of advanced manipulation techniques, already standard in atomic physics. These are not straightforward for molecules, and for charged molecules have not yet been demonstrated [1]. In this respect, trapped cold HD$^+$ is also a useful model system. We performed THz and laser spectroscopy as well as quantum state manipulation of this molecular ion species. The ions are trapped in an ion trap and sympathetically cooled by laser-cooled atomic ions (Be$^+$) in order to reduce spectrosopic line broadening. A novel frequency-comb-based, continuous-wave 5 $\mu$m laser spectrometer was employed and spectroscopy at the Doppler-limit was performed [2]. To our knowledge, the achieved spectral resolution is the highest obtained so far in the optical domain on a molecular ion species. We were thus able to optically resolve the hyperfine structure. We found agreement of the measured absolute transition frequencies and of the hyperfine splittings with ab-initio theory, the experimental inaccuracy being up to approx. $1 \cdot 10^{-9}$ [3]. This work also represents the most precise test yet of the ab-initio theory of any molecule. We demonstrated addressing of individual hyperfine states of ro-vibrational levels by excitation of individual hyperfine transitions, and controlled transfer of population into a selected hyperfine state [3]. We also report on the first observation of the fundamental pure rotational transition in this molecule [4] and on ongoing developments towards more complete manipulation of the hyperfine states.\\[4pt] [1] B. Roth and S. Schiller, in: Cold Molecules, R. Krems et al. eds., (Taylor and Francis, Boca Raton, FL, 2009).\\[0pt] [2] U. Bressel, I. Ernsting, S. Schiller, Opt. Lett. 37, 918 (2012).\\[0pt] [3] U. Bressel, A. Borodin, J. Shen, M. Hansen, I. Ernsting, S. Schiller, Phys. Rev. Lett. 108, 183003 (2012).\\[0pt] [4] J. Shen, A. Borodin, M. Hansen, and S. Schiller, Phys. Rev. A 85, 032519 (2012). [Preview Abstract] |
Wednesday, June 5, 2013 9:30AM - 10:00AM |
G2.00004: Polarizability shifts and body-frame electric-dipole moments of molecular ions in a Penning trap Invited Speaker: Edmund Myers In a Penning trap the cyclotron frequency of a polarizable ion is perturbed by the Stark interaction of the ion with the motional electric field. For polar molecular ions, which have adjacent rotational levels of opposite parity, these state-dependent cyclotron frequency shifts can be particularly large - especially for the lowest rotational levels, which are occupied in a Penning trap at 4.2K. These polarizability shifts complicate precision atomic mass measurement, but can also be used to measure body-frame dipole moments of molecular ions, which are difficult to measure by other means. [Preview Abstract] |
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