48 research outputs found
Theory of the n=2 levels in muonic deuterium
The present knowledge of Lamb shift, fine- and hyperfine structure of the
and states in muonic deuterium is reviewed in
anticipation of the results of a first measurement of several
transition frequencies in muonic deuterium (). A term-by-term
comparison of all available sources reveals reliable values and uncertainties
of the QED and nuclear structure-dependent contributions to the Lamb shift,
which are essential for a determination of the deuteron rms charge radius from
. Apparent discrepancies between different sources are resolved,
in particular for the difficult two-photon exchange contributions. Problematic
single-sourced terms are identified which require independent recalculation.Comment: 26 pages, add missing feynman diagrams (Fig. 3), renumber items (Tab.
IV), correct a sum (column 5, Tab. IV
Oxidative phosphonylation of aromatic compounds
Aryl phosphonates can be prepared in good yield from the respective arenes and tri- or dialkyphosphites by either chemical or anodic oxidation. The anodic oxidation proceeds either via phosphinium radical cations, which then attack the arenes electrophilically, or via arene radical cations, which add the trialkylphosphite as nucleophile. Aryl phosphonates are also obtained in good yield by chemical oxidation with peroxodisulfate/AgNO3 in acetonitrile/water or glacial acetic acid. The diethylphosphinium radical cation, formed from diethylphosphite by oxidation with Ag(II), is supposed to be the reactive species in this process. Raising the silver salt concentration leads to an increase in polyphosphonylation. Selectivity ratios were determined for the oxidative phosphonylation process
Observation of Long-Lived Muonic Hydrogen in the 2S State
The kinetic energy distribution of ground state muonic hydrogen atoms
mu-p(1S) is determined from time-of-flight spectra measured at 4, 16, and 64
hPa H2 room-temperature gas. A 0.9 keV-component is discovered and attributed
to radiationless deexcitation of long-lived mu-p(2S) atoms in collisions with
H2 molecules. The analysis reveals a relative population of about 1%, and a
pressure-dependent lifetime (e.g. (30.4 +21.4 -9.7) ns at 64 hPa) of the
long-lived mu-p(2S) population, equivalent to a 2S-quench rate in mu-p(2S) + H2
collisions of (4.4 +2.1 -1.8) 10^11 s^-1 at liquid hydrogen density.Comment: 4 pages, 2 figures, accepted for publication in Physical Review
Letter
Feasibility of Coherent xuv Spectroscopy on the 1S-2S Transition in Singly Ionized Helium
The 1S-2S two-photon transition in singly ionized helium is a highly interesting candidate for precision tests of bound-state quantum electrodynamics (QED). With the recent advent of extreme ultraviolet frequency combs, highly coherent quasi-continuous-wave light sources at 61 nm have become available, and precision spectroscopy of this transition now comes into reach for the first time. We discuss quantitatively the feasibility of such an experiment by analyzing excitation and ionization rates, propose an experimental scheme, and explore the potential for QED tests
Improved X-ray detection and particle identification with avalanche photodiodes
Avalanche photodiodes are commonly used as detectors for low energy x-rays.
In this work we report on a fitting technique used to account for different
detector responses resulting from photo absorption in the various APD layers.
The use of this technique results in an improvement of the energy resolution at
8.2 keV by up to a factor of 2, and corrects the timing information by up to 25
ns to account for space dependent electron drift time. In addition, this
waveform analysis is used for particle identification, e.g. to distinguish
between x-rays and MeV electrons in our experiment.Comment: 6 pages, 6 figure
Theory of the 2S-2P Lamb shift and 2S hyperfine splitting in muonic hydrogen
The 7 standard deviations between the proton rms charge radius from muonic
hydrogen and the CODATA-10 value from hydrogen spectroscopy and
electron-scattering has caused considerable discussions. Here, we review the
theory of the 2S-2P Lamb shift and 2S hyperfine splitting in muonic hydrogen
combining the published contributions and theoretical approaches. The
prediction of these quantities is necessary for the determination of both
proton charge and Zemach radii from the two 2S-2P transition frequencies
measured in muonic hydrogen.Comment: 20 pages with 3 Tables summarising the contributions to the muonic
hydrogen Lamb shift and hyperfine splittin
The Lamb shift in muonic hydrogen and the proton radius
By means of pulsed laser spectroscopy applied to muonic hydrogen (ÎŒâ p) we have measured the 2S F = 1 1/2 â 2PF = 2 3/2 transition frequency to be 49881.88(76) GHz. By comparing this measurement with its theoretical prediction based on bound-state QED we have determined a proton radius value of rp = 0.84184 (67) fm. This new value is an order of magnitude preciser than previous results but disagrees by 5 standard deviations from the CODATA and the electronproton scattering values. An overview of the present effort attempting to solve the observed discrepancy is given. Using the measured isotope shift of the 1S-2S transition in regular hydrogen and deuterium also the rms charge radius of the deuteron rd = 2.12809 (31) fm has been determined. Moreover we present here the motivations for the measurements of the ÎŒ 4He + and ÎŒ 3He + 2S-2P splittings. The alpha and triton charge radii are extracted from these measurements with relative accuracies of few 10 â 4. Measurements could help to solve the observed discrepancy, lead to the best test of hydrogen-like energy levels and provide crucial tests for few-nucleon ab-initio theories and potentials
The Lamb shift in muonic hydrogen
The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the 2S1/2F=1â2P3/2F=2 energy splitting (Pohl et al., Nature, 466, 213 (2010)) in ÎŒp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of rpâ=â0.841â84â(67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1Sâ2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, Rââ=â10â973â731.568â160â(16) mâ»Âč and the rms charge radius of the deuteron rdâ=â2.128â09â(31) fm
The size of the proton and the deuteron
We have recently measured the 2S1/2âŒÂč â 2P3/2 ⌠ÂČ energy splitting in the muonic hydrogen atom ÎŒp to be 49881.88 (76) GHz. Using recent QED calculations of the fine-, hyperfine, QED and finite size contributions we obtain a root-mean-square proton charge radius of rp = 0.84184 (67) fm. This value is ten times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp = 0.8768 (69) fm. The source of this discrepancy is unknown. Using the precise measurements of the 1S-2S transition in regular hydrogen and deuterium and our value of rp we obtain improved values of the Rydberg constant, Râ = 10973731.568160 (16) mâ»Âčand the rms charge radius of the deuteron rd = 2.12809 (31) fm
The Lamb shift in muonic hydrogen 1
Abstract: The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the energy splitting (Pohl et al., Nature, 466, 213 (2010)) in mp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a rootmean-square proton charge radius of r p = 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of r p . The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S-2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R ? = 10 973 731.568 16