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[en] High precision measurements of the fine structure intervals in the 1s2p3PJ state of helium have the potential to provide an atomic physics measurement of the fine structure constant α. The interpretation of measurements at this level of accuracy (±10 kHz or better), requires an extension of the known relativistic and QED corrections to include terms of order α7. Starting from a fully covariant relativistic formalism, the authors have now completed an evaluation of all terms up to order α7 ln α. Equivalent nonrelativistic operators are derived whose expectation values can be calculated to high precision and added to previous results. The predicted transition frequencies are ν01=29 616 914.4 kHz and ν12 = 2 291 182.2 kHz. The additional uncertainty due to terms of O(α7) not yet included is estimated to be ±20 kHz. Work on these terms is in progress. A comparison with recent high precision measurements will be made
[en] The theory of the coherent creation of pairs by photon in the alignment crystal under conditions when the created electron and positron moving in the axial channeling regime is developed. In this case combined effect takes place which consist in a broadening of the width and changing of the shape and to appearance of the fine structure of the coherent peaks.
[en] The fine structure found by Gu, Hill and Rosenwald between asymptotic theory eigenfrequencies and the observed eigenfrequencies reported by Hill and Gu is interpreted as the result of conditions not being met for the applicability of asymptotic theory at one or more radii in the solar interior. From an inversion of the observed fine structure, reasonably good agreement is obtained between observation and theory for either a localized perturbation in internal structure at r/R ∼ 0.06 or at r/R ∼ 0.23. The latter solution is, however, the better one. The amplitude of the perturbation in the mean molecular weight required to produce the fine structure is also inferred. 11 refs., 2 figs
[en] Doppler-free two-photon laser spectroscopy has been employed for excited transitions between the 1S and 2S states in muonium. An unambiguous signal could be observed. The frequency interval was determined to be Δν1S-2S = 2 455 529 002(33)(46) MHz, where the first error arises from statistics and the second one is due to systematic effects which mainly are related to the properties of the high power pulsed laser system. There is agreement with a prior less accurate independent experiment at KEK and with QED theory within two standard deviations. The Lamb shift contributions are tested at the 8 · 10-3 level. The muonium-hydrogen and muonium-deuterium isotope shifts of the 1S-2S transition have a high potential for a precise mass determination of the positive muon. The experiment yields at present m1S-2Sμ = 105.658 80(29)(43) MeV/c2