Measurement of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mi mathvariant="italic">s</mml:mi><mml:mi>−</mml:mi><mml:mn>2</mml:mn><mml:mi mathvariant="italic">s</mml:mi></mml:math>Energy Interval in Muonium

Meyer, B. S.; Bagayev, S. N.; Baird, P E G; Bakule, Pavel; Boshier, M. G.; Breitruck, A.; Cornish, Simon L.; Dychkov, S; Eaton, G. H.; Großmann, A.; Hubl, D; Hughes, V. W.; Jungmann, Klaus-Peter; Lane, I.C.; Liu, Yi-Wei; Lucas, David M.; Matyugin, Yu. A.; Merkel, J.; Putlitz, G. zu; Reinhard, S.; Sandars, P. G. H.; Santra, Robin; Schmidt, PV; Scott, C.A.; Toner, W.T.; Towrie, Michael; Träger, K.; Willmann, Lorenz; Yakhontov,

doi:10.1103/physrevlett.84.1136

Cited by 117 publications

(51 citation statements)

References 26 publications

(21 reference statements)

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“…Since the first measurement by Lamb and Retherford, QED contributions to energy levels in atoms are referred to as "Lamb shifts. " The theory has been elaborately tested and confirmed by experiments in various bound systems, ranging from atomic hydrogen [6,7] and helium [8][9][10], via one-electron heavy-ion systems [11], exotic atomic systems such as positronium [12] and muonium [13], to one-electron molecular ions [14,15], while recently a test of QED has also been reported in a neutral molecule [16]. Tests have also been performed on the anomalous magnetic dipole moment of the electron ("g-2"), so that in fact QED can now be used to derive a new value for the fine structure constant from such a measurement [17].…”

Section: Introductionmentioning

confidence: 95%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1 P 1 states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p 1 P 1 states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved 4 He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the 4 He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order mα 6 and m 2 /Mα 5 , but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

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Section: Introductionmentioning

confidence: 95%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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“…Experiments with atoms that do not exist naturally can be powerful tools for the study of fundamental physics [ 1,2,3,4,5 ]. A major experimental challenge for such studies is the short intrinsic lifetimes of the exotic atoms.…”

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confidence: 99%

Confinement of antihydrogen for 1,000 seconds

et al. 2011

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Reported trapping times of magnetically confined (matter) atoms range from <1 s in the first, room temperature, traps [ 18 ] to 10 to 30 minutes in cryogenic devices [ 19,20,21,22 ]. However, antimatter atoms can annihilate on background gases. Also, the loading of our trap (i.e., anti-atom production via merging of cold plasmas) is different from that of ordinary atom traps, and the loading dynamics could adversely affect the trapping and orbit dynamics. Mechanisms exist for temporary magnetic trapping of particles (e.g., in quasi-stable trapping orbits [ 23 ], or in excited internal states [ 24 ]); such particles could be short-lived with a trapping time of a few 100 ms. Thus, it is not a priori obvious what trapping time should be expected for antihydrogen. 5In this article, we report the first systematic investigations of the characteristics of trapped antihydrogen. These studies were made possible by significant advances in our trapping techniques subsequent to Ref. [ 17 ]. These developments, including incorporation of evaporative antiproton cooling[ 25 ] into our trapping operation, and optimisation of autoresonant mixing [ 26 ], resulted in up to a factor of five increase in the number of trapped atoms per attempt. A total sample of 309 trapped antihydrogen annihilation events was studied, a large increase from the previously published 38 events.Here we report trapping of antihydrogen for 1000 s, extending earlier results [ 17 ] by nearly four orders of magnitude. Further, we have exploited the temporal and spatial resolution of our detector system to perform a detailed analysis of the antihydrogen release process, from which we infer information on the trapped antihydrogen kinetic energy distribution.The ALPHA antihydrogen trap [ 27,28 ] is comprised of the superposition of a Penning trap for antihydrogen production and a magnetic field configuration that has a three-dimensional minimum in magnitude (Fig. 1). For ground-state antihydrogen, our trap well-depth is 0.54 K (in temperature units).The large discrepancy in the energy scales between the magnetic trap depth (~50 eV), and the characteristic energy scale of the trapped plasmas (a few eV) presents a formidable challenge to trapping neutral anti-atoms. antiprotons at ~100K, with radius 0.4 mm and density 7x10 7 cm -3 is prepared for mixing with positrons.Independently, the positron plasma, accumulated in a Surko-type buffer gas accumulator [ 33 ,34 ], is transferred to the mixing region, and is also radially compressed. The magnetic trap is then energized, 6 and the positron plasma is cooled further via evaporation, resulting in a plasma with a radius of 0.8 mm and containing 1x10 6 positrons at a density of 5x10 7 cm -3 and a temperature of ~40 K. The silicon vertex detector, surrounding the mixing trap in three layers (Fig. 1 a) ]. Knowledge of annihilation positions also provides sensitivity to the antihydrogen energy distribution, as we will show.In Table 1 and Fig. 2, we present the results for a series of measurements, wherein the confinemen...

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“…We measured the frequency chirp ν c by superimposing the pulsed and cw seed beams on a photodiode and measuring the heterodyne beat signal. An electro-optic modulator (EOM) was used to apply a frequency shift to the seed laser which canceled the chirp ν c [25,26]. The linewidth of the pulsed laser beam was typically around ∼ 60 MHz [4].…”

Section: Continuous-wave Pulse-amplified Dye Lasersmentioning

confidence: 99%