Illuminating the proton radius conundrum: the μHe+ Lamb shiftThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

We plan to measure several 2S–2P transition frequencies in μ4He+ and μ3He+ by means of laser spectroscopy with an accuracy of 50 ppm. This will lead to a determination of the corresponding nuclear rms charge radii with a relative accuracy of 3 × 10−4, limited by the uncertainty of the nuclear polarization contribution. First, these measurements will help to solve the proton radius puzzle. Second, these very precise nuclear radii are benchmarks for ab initio few-nucleon theories and potentials. Finally when combined with an ongoing measurement of the 1S–2S transition in He+, these measurements will lead to an enhanced bound-state QED test of the 1S Lamb shift in He+.

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The Rydberg constant and proton size from atomic hydrogen

Science ◽

10.1126/science.aah6677 ◽

2017 ◽

Vol 358 (6359) ◽

pp. 79-85 ◽

Cited By ~ 160

Author(s):

Axel Beyer ◽

Lothar Maisenbacher ◽

Arthur Matveev ◽

Randolf Pohl ◽

Ksenia Khabarova ◽

...

Keyword(s):

Atomic Hydrogen ◽

Quantum Interference ◽

Muonic Hydrogen ◽

Mean Square ◽

Charge Radii ◽

The Core ◽

Proton Radius ◽

Rydberg Constant ◽

Proton Radius Puzzle ◽

Good Agreement

At the core of the “proton radius puzzle” is a four–standard deviation discrepancy between the proton root-mean-square charge radii (rp) determined from the regular hydrogen (H) and the muonic hydrogen (µp) atoms. Using a cryogenic beam of H atoms, we measured the 2S-4P transition frequency in H, yielding the values of the Rydberg constantR∞= 10973731.568076(96) per meterandrp= 0.8335(95) femtometer. Ourrpvalue is 3.3 combined standard deviations smaller than the previous H world data, but in good agreement with the µp value. We motivate an asymmetric fit function, which eliminates line shifts from quantum interference of neighboring atomic resonances.

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Theoretical progress in the H2+ molecular ion: towards electron to proton mass ratio determinationThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

Canadian Journal of Physics ◽

10.1139/p10-065 ◽

2011 ◽

Vol 89 (1) ◽

pp. 103-107 ◽

Cited By ~ 10

Author(s):

J.-Ph. Karr ◽

L. Hilico ◽

V. I. Korobov

Keyword(s):

High Resolution ◽

Mass Ratio ◽

Theoretical Determination ◽

Atomic Systems ◽

The Road ◽

Theoretical Progress ◽

Proton Mass ◽

Accuracy Level ◽

Ratio Determination

High resolution ro-vibrational spectroscopy of H 2+ or HD+ can lead to a significantly improved determination of the electron to proton mass ratio me/mp if the theoretical determination of transition frequencies becomes sufficiently accurate. We report on recent theoretical progress in the description of the hyperfine structure of H 2+ , as well as first steps in the evaluation of radiative corrections at order mα7. Completion of the latter calculation should allow us to reach the projected 10−10 accuracy level and open the road to mass ratio determination.

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Gating Competence of Constitutively Open CLC-0 Mutants Revealed by the Interaction with a Small Organic Inhibitor

The Journal of General Physiology ◽

10.1085/jgp.200308784 ◽

2003 ◽

Vol 122 (3) ◽

pp. 295-306 ◽

Cited By ~ 52

Author(s):

Sonia Traverso ◽

Laura Elia ◽

Michael Pusch

Keyword(s):

Chloride Channels ◽

Bound State ◽

Side Chain ◽

Pore Channel ◽

Kinetic Properties ◽

Wild Type ◽

High Affinity ◽

Critical Residue ◽

Fast Gating

Opening of CLC chloride channels is coupled to the translocation of the permeant anion. From the recent structure determination of bacterial CLC proteins in the closed and open configuration, a glutamate residue was hypothesized to form part of the Cl−-sensitive gate. The negatively charged side-chain of the glutamate was suggested to occlude the permeation pathway in the closed state, while opening of a single protopore of the double-pore channel would reflect mainly a movement of this side-chain toward the extracellular pore vestibule, with little rearrangement of the rest of the channel. Here we show that mutating this critical residue (Glu166) in the prototype Torpedo CLC-0 to alanine, serine, or lysine leads to constitutively open channels, whereas a mutation to aspartate strongly slowed down opening. Furthermore, we investigated the interaction of the small organic channel blocker p-chlorophenoxy-acetic acid (CPA) with the mutants E166A and E166S. Both mutants were strongly inhibited by CPA at negative voltages with a >200-fold larger affinity than for wild-type CLC-0 (apparent KD at −140 mV ∼4 μM). A three-state linear model with an open state, a low-affinity and a high-affinity CPA-bound state can quantitatively describe steady-state and kinetic properties of the CPA block. The parameters of the model and additional mutagenesis suggest that the high-affinity CPA-bound state is similar to the closed configuration of the protopore gate of wild-type CLC-0. In the E166A mutant the glutamate side chain that occludes the permeation pathway is absent. Thus, if gating consists only in movement of this side-chain the mutant E166A should not be able to assume a closed conformation. It may thus be that fast gating in CLC-0 is more complex than anticipated from the bacterial structures.

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