Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session N02: Advanced Laser Spectroscopy for Fundamental Physics |
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Sponsoring Units: GPMFC Chair: Tom Kirchner, York University Room: Wisconsin Center 101AB |
Thursday, May 30, 2019 8:00AM - 8:30AM |
N02.00001: A high-precision measurement of the $n$=2 atomic hydrogen Lamb shift Invited Speaker: E. A. Hessels A precise microwave measurement of the $n$=2 Lamb shift of atomic hydrogen is presented. The measurement is performed using the new frequency-offset separated oscillatory field (FOSOF) technique. The rms proton charge radius can be determined by comparing the current measurement to existing precise QED theory. Since the measurement made in 2010 of the $n$=2 Lamb shift of muonic hydrogen, there has been a large unexplained discrepancy between the proton radius determinations using electrons and those determined using muons. This discrepancy has been referred to as the proton size puzzle, and the current measurement helps to resolve that puzzle. [Preview Abstract] |
Thursday, May 30, 2019 8:30AM - 9:00AM |
N02.00002: Laser spectroscopy of a nucleus: The search for the isomeric transition in thorium-229 Invited Speaker: Eric Hudson In 1976, Kroger and Reich established the existence of a low-lying nuclear excited state in Th-229 through the spectroscopy of gamma rays emitted following the alpha decay of U-233. The prospects of a laser-accessible nuclear transition touched off a flurry of proposals to utilize this apparently unique nuclear transition as a sensitive probe of both nuclear structure and chemical environment, to constrain the variability of the fundamental constants, to demonstrate a gamma-ray laser, and to construct a clock with unprecedented performance. However, while the last forty years have witnessed the confirmation of the existence of the state and a refinement of its energy to around 8 eV, measurements have yet to measure the transition energy precisely enough to allow the dream of laser spectroscopy of a nucleus. To directly measure this transition energy we have developed two experimental efforts. The first uses thorium-doped VUV transparent crystals as targets to observe the transition via laser-induced nuclear fluorescence. The second, in collaboration with the NIST-Boulder group, uses superconducting nanowires to measures the energy of internal conversion electrons produced in decay of the isomeric state. We will report the status of these experiments. [Preview Abstract] |
Thursday, May 30, 2019 9:00AM - 9:30AM |
N02.00003: 1S-3S hydrogen spectroscopy with cw laser Invited Speaker: Francois Nez High resolution spectroscopy of the hydrogen atom plays a key role in testing the theory of quantum electrodynamics, and in the determination of fundamental constants, such as the Rydberg constant or the proton charge radius. Since 2010, a disagreement has been found between the proton radius deduced from the spectroscopy of muonic hydrogen and the CODATA recommended value, relying on experiments conducted on electronic hydrogen. To date still unsolved, this proton radius puzzle was even recently deepened by new contradictory results, obtained at MPQ (Garching) and LKB (Paris). Paris’s experiment aims at measuring the 1S–3S transition frequency of the hydrogen atom. It is based on a Doppler-free two-photon excitation, at 205 nm, of an effusive beam of hydrogen at room temperature. Referenced to the Cs clock of the LNE-SYRTE (Paris), it allows to reach a relative uncertainty below one part-per-trillion. I will present this experiment, our latest results, and our current efforts to shed light on the proton radius puzzle. To this end, we plan to cool down our current hydrogen beam and perform a new determination of the 1S-3S transition frequency in H and D. Thereafter, in order to investigate possible systematic effects related to the configuration of our hydrogen beam, an entirely new effusive beam is to be build, pumped by an oil-free vacuum system. [Preview Abstract] |
Thursday, May 30, 2019 9:30AM - 10:00AM |
N02.00004: Optical clocks based on molecular vibrations as probes of time-varying mass ratios Invited Speaker: David Hanneke Some models of quantum gravity and some classes of dark matter predict temporal changes in the fundamental constants. Changes in the ``constants'' could manifest themselves as drifts or oscillations in their values. Molecular vibrations and rotations involve the motion of the nuclei themselves. They thus provide a system that is relatively simple to model while also sensitive to the ratio of the nuclear mass -- and thereby the proton mass -- to the electron mass. There are several proposed approaches to using molecules in these searches. The extra degrees of freedom in molecules that enable these searches also bring challenges to their precise control. This talk will give an overview of ongoing work in this area as well as details about experiments at Amherst College with singly ionized diatomic oxygen molecules, both in a beam and a trap.\\ \\This work is supported by the NSF (RUI PHY-1806223, CAREER PHY-1255170). [Preview Abstract] |
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