Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session C7: Fundamental Constants and Symmetries |
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Chair: Marianna Safronova, University of Delaware Room: 313 |
Tuesday, June 6, 2017 2:00PM - 2:12PM |
C7.00001: Measuring the fine structure constant with Bragg diffraction and Bloch oscillations Richard Parker, Chenghui Yu, Weicheng Zhong, Brian Estey, Holger Müller We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations [1]. In this new scheme, we have achieved a resolution of δα/α=0.25ppb in the fine structure constant measurement, which gives over 10 million radians of phase difference between freely evolving matter waves. We have suppressed many systematic effects known in most atom interferometers with Raman beam splitters such as light shift, Zeeman effect shift as well as vibration. We have also simulated multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implemented spatial filtering to further suppress systematic effects [2]. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics. [1] Estey et al., PRL 115, 083002 (2015), [2] Parker et al., PRA 053618 (2016). [Preview Abstract] |
Tuesday, June 6, 2017 2:12PM - 2:24PM |
C7.00002: Scaling up precision in an Ytterbium BEC contrast interferometer for photon recoil and $\alpha$. Benjamin Plotkin-Swing, Daniel Gochnauer, Katherine McAlpine, Subhadeep Gupta Building on our earlier demonstration [1], we are now operating a second-generation Ytterbium (Yb) Bose-Einstein condensate (BEC) contrast interferometer. The device is designed to measure h/m, where h is Planck's constant and m is the mass of a Yb atom, in order to determine the fine structure constant $\alpha$. The use of the non-magnetic Yb atom and the symmetric geometry of the interferometer make the measurement immune to several error sources. The narrow momentum and position spread of a BEC help improve the coherence length and signal strength of our measurement. A key advantage of the contrast interferometer is that the total phase accumulation and therefore the measurement sensitivity scales quadratically with the momentum separation of the interfering states. We have demonstrated the laser pulse atom-optics required to increase the momentum splitting, including using Bloch oscillations to impart 200 photon recoils with .5\% atom loss per recoil. We have implemented the first steps in applying these high momentum transfer techniques to our interferometer, and will report on our progress towards achieving quadratically increased precision. \newline \newline [1] Alan O. Jamison, Benjamin Plotkin-Swing, and Subhadeep Gupta, Phys. Rev. A 90, 063606 (2014) [Preview Abstract] |
Tuesday, June 6, 2017 2:24PM - 2:36PM |
C7.00003: Tune-out wavelength for the $\mathbf{1s2s\;^3S - 1s3p\;^3P}$ transition of helium: relativistic effects Gordon W.F. Drake, Jacob Manalo The tune-out wavelength is the wavelength at which the frequency dependent polarizability of an atom vanishes. It can be measured to very high precision by means of an interferometric comparison between two beams. This paper is part of a joint theoretical/ experimental project with K. Baldwin et al.\ (Australian National University) [1] and L.-Y. Tang et al.\ (Wuhan Institute of Physics and Mathematics) [2] to perform a high precision comparison between theory and experiment as a probe of atomic structure, including relativistic and quantum electrodynamic effects. We will report the results of calculations for the tune-out wavelength that is closest to the $1s2s\;^3S - 1s3p\; ^3P$ transition of $^4$He. Our result for the $M = 0$ magnetic substate, obtained with a fully correlated Hylleraas basis set, is $413.079\,958\,51(12)$ nm. This includes a leading relativistic contribution of $-0.059\,218\,5(16)$ nm from the Breit interaction as a perturbation, and a relativistic recoil contribution of $-0.000\,044\,47(17)$ nm. The results will be compared with recent relativistic CI calculations [2]. \newline [1] B. M. Henson et al., Phys.\ Rev.\ Lett.\ {\bf 115}, 043004 (2015).\newline [2] Y.-H. Zhang et al., Phys.\ Rev.\ A {\bf 93}, 052516 (2016). [Preview Abstract] |
Tuesday, June 6, 2017 2:36PM - 2:48PM |
C7.00004: Towards Precision Measurement of the 2$^{\mathrm{1}}$S$_{\mathrm{0\thinspace }}$-3$^{\mathrm{1}}$D$_{\mathrm{2}}$ Two-Photon Transition in Atomic Helium. Yi-Jan Huang, Yu-Chan Guan, Te-Hwei Suen, Li-Bang Wang, Jow-Tsong Shy We intend to accurately measure the frequency for 2S-3D two-photon transition and to deduce the 2S ionization energy to an accuracy below 100 kHz from the theoretical calculation of the 3D state. In this talk, we present a precision measurement of the 2$^{\mathrm{1}}$S$_{\mathrm{0}}$ -3$^{\mathrm{1}}$D$_{\mathrm{2}}$ two-photon transition in atomic helium at 1009 nm. A master oscillator power amplifier (MOPA) is seeded by an external cavity diode laser (ECDL) is constructed to generate more than 700 mW laser power with TEM00 beam profile at 1009 nm. To observe the two-photon transition, a helium cell is placed inside a power enhancement optical cavity and the helium atoms at 2$^{\mathrm{1}}$S metastable level are prepared by a pulsed RF discharge and monitor the 668 nm 3$^{\mathrm{1}}$D$_{\mathrm{2}}$ to 2$^{\mathrm{1}}$P$_{\mathrm{1}}$ fluorescence after RF discharge is turned off . The absolute frequency metrology of the ECDL is carried out by an Er-fiber optical frequency comb (OFC). The two-photon spectrum is obtained by tuning the repetition frequency of the OFC. The 2$^{\mathrm{1}}$S$_{\mathrm{0\thinspace }}$-3$^{\mathrm{1}}$D$_{\mathrm{2}}$ frequency is determined to be 594414291.967 (80) MHz in He-4. More results will be presented at the annual meeting. [Preview Abstract] |
Tuesday, June 6, 2017 2:48PM - 3:00PM |
C7.00005: Precision spectroscopy of the 2S-4P transition in atomic hydrogen Lothar Maisenbacher, Axel Beyer, Arthur Matveev, Alexey Grinin, Randolf Pohl, Ksenia Khabarova, Nikolai Kolachevsky, Theodor W. H\"ansch, Thomas Udem Precision measurements of atomic hydrogen have long been successfully used to extract fundamental constants and to test bound-state QED. However, both these applications are limited by measurements of hydrogen lines other than the very precisely known 1S-2S transition. Moreover, the proton r.m.s.$\,$charge radius $r_p$ extracted from electronic hydrogen measurements currently disagrees by 4\,$\sigma$ with the much more precise value extracted from muonic hydrogen spectroscopy. We have measured the 2S-4P transition in atomic hydrogen using a cryogenic beam of hydrogen atoms optically excited to the initial 2S state\footnote{A. Beyer et al., Physica Scripta 165 014030 (2015)}. The first order Doppler shift of the one-photon 2S-4P transition is suppressed by actively stabilized counter-propagating laser beams and time-of-flight resolved detection\footnote{A. Beyer et al., Optics Express 24, 17470 (2016)}. Quantum interference between excitation paths can lead to significant line distortions in our system. We use an experimentally verified, simple line shape model to take these distortions into account. With this, we can extract a new value for $r_p$ and the Rydberg constant $R_\infty$ with comparable accuracy as the combined previous H world data. [Preview Abstract] |
Tuesday, June 6, 2017 3:00PM - 3:12PM |
C7.00006: Forbidden M1 and E2 transitions in monovalent atoms and ions W. R. Johnson, U. I. Safronova, M. S. Safronova We carried out a systematic high-precision relativistic study of the forbidden magnetic-dipole and electric-quadrupole transitions in Ca$^+$, Rb, Sr$^+$, Cs, Ba$^+$, Fr, Ra$^+$, Ac$^{2+}$ and Th$^{3+}$. This work is motivated by the importance of these transitions for tests of fundamental physics and precision measurements. The relative importance of the relativistic, correlation, Breit correction and contributions of negative-energy states is investigated. Recommended values of reduced matrix elements are presented together with their uncertainties. The matrix elements and resulting lifetimes are compared with other theoretical values and with experiment where available. [Preview Abstract] |
Tuesday, June 6, 2017 3:12PM - 3:24PM |
C7.00007: Near-degeneracy in Excited Vibrational States of $^{\mathrm{207}}$PbF Richard Mawhorter, Alexander Nguyen, Yongrak Kim, Andreas Biekert, Trevor Sears, Jens-Uwe Grabow, A.D. Kudashov, L.V. Skripnikov, A.V. Titov, A.N. Petrov High-resolution Fourier transform microwave (FTMW) spectroscopy studies of $^{\mathrm{207}}$PbF [1,2] have demonstrated the near-degeneracy of two levels of opposite parity. These have attracted attention for the study of parity violation effects and the variation of fundamental constants [3] using $^{\mathrm{207}}$PbF. Further theoretical work has improved our detailed understanding of both $^{\mathrm{207}}$PbF and $^{\mathrm{208}}$PbF [4], and furthermore recently indicated that the finely split $+$/- parity levels grow monotonically closer for higher vibrational states. Our experimental results for v $=$ 0-3 confirm this, and are in excellent agreement with our extended theoretical calculations up to v $=$ 4; both will be presented. TJS acknowledges support from Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, supported by its Division of Chemical Sciences, Geosciences and Biosciences within the Office of Basic Energy Sciences., as do RM, AB, YK, {\&} AN from Pomona College {\&} J-UG from the Deutsche Forschungsgemeinschaft (DFG). $^{\mathrm{1}}$ L.D. Alphei, et al., Phys. Rev. A \textbf{83}, 040501 (R) (2011). $^{\mathrm{2}}$ R. Mawhorter,\textit{ et al}., Phys. Rev. A \textbf{84}, 022508 (2011). $^{\mathrm{3}}$ V.V. Flambaum, et al., Phys. Rev. A \textbf{88}, 052124 (2013). $^{\mathrm{4}}$ A.N. Petrov, \textit{et al}., Phys. Rev. A \textbf{88}, 010501 (R) (2013). [Preview Abstract] |
Tuesday, June 6, 2017 3:24PM - 3:36PM |
C7.00008: Isotope shifts in the $7S\rightarrow 8S$ transition of francium: measurements and comparison to ab-initio theory Mukut Kalita, John Behr, Alexandre Gorelov, Matthew Pearson, Austin Dehart, Gerald Gwinner, Michael Kossin, Seth Aubin, Eduardo Gomez, Luis A. Orozco, Vladimir Dzuba, Victor Flambaum, Marianna Safronova The Standard Model can be tested at low energies by probing parity non-conservation (PNC) effects in atomic systems. At the francium trapping facility at TRIUMF, we are developing a Stark interference experiment to probe PNC in neutral francium atoms using the $7S\rightarrow 8S$ atomic transition. We have observed this transition in francium using two-photon spectroscopy. This allows the extraction of the isotope shifts of the $8S$ state. We have measured the shifts on five isotopes $^{208,209,210,211,213}$Fr of cold trapped atoms. Using our previously measured isotope shifts of the 7$P_{1/2}$ level we can extract the ratio of field shift constants and the relation between specific mass shift constants. The experimental results will be compared to recent ab-initio calculations. [Preview Abstract] |
Tuesday, June 6, 2017 3:36PM - 3:48PM |
C7.00009: ABSTRACT WITHDRAWN |
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