We use Bloch oscillations to transfer coherently many photon momenta to atoms. Then we can measure accurately the ratio h/m_Rb and deduce the fine structure constant alpha. The velocity variation due ...to the Bloch oscillations is measured thanks to Raman transitions. In a first experiment, two Raman $\pi$ pulses are used to select and measure a very narrow velocity class. This method yields to a value of the fine structure constant alpha^{-1}= 137.035\,998\,84\,(91) with a relative uncertainty of about 6.6 ppb. More recently we use an atomic interferometer consisting in two pairs of pi/2 pulses. We present here the first results obtained with this method.
The Lamb-shift experiment in muonic hydrogen (μ
-
p) aims to measure the energy difference between the
atomic levels to a precision of 30 ppm. This would allow the r.m.s. proton charge radius r
p
to ...be deduced to a precision of 10
-3
and open a way to check bound-state quantum electrodynamics (QED) to a level of 10
-7
. The poor knowledge of the proton charge radius restricts tests of bound-state QED to the precision level of about 6 × 10
-6
, although the experimental data themselves (Lamb-shift in hydrogen) have reached a precision of × 10
-6
. Values for r
p
not depending on bound-state QED results from electron scattering experiments have a surprisingly large uncertainty of 2%. In our Lamb-shift experiment, low-energy negative muons are stopped in low-density hydrogen gas, where, following the μ
-
atomic capture and cascade, 1% of the muonic hydrogen atoms form the metastable 2S state with a lifetime of about 1 μs. A laser pulse at λ ≈ 6 μm is used to drive the 2S → 2P transition. Following the laser excitation, we observe the 1.9 keV X-ray being emitted during the subsequent de-excitation to the 1S state using large-area avalanche photodiodes. The resonance frequency and, hence, the Lamb shift and the proton charge radius are determined by measuring the intensity of the X-ray fluorescence as a function of the laser wavelength. The results of the run in December 2003 were negative but, nevertheless, promising. One by-product of the 2003 run was the first observation of the short-lived 2S component in muonic hydrogen. Currently, improvements in the laser-system, the experimental apparatus, and the data acquisition are being implemented. PACS Nos.: 36.10.Dr, 14.20.Dh, 42.62.Fi
High resolution spectroscopy of the hydrogen atom takes on particular importance in the new SI, as it allows to accurately determine fundamental constants, such as the Rydberg constant and the proton ...charge radius. Recently, the second most precisely measured transition frequency in hydrogen, 1S - 3S, was obtained in our group. In the context of the Proton Radius Puzzle, this result calls for further investigation.
The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the
2S
1/2
F=1
-2P
3/2
F=2
energy splitting (Pohl et al., Nature,
466
, 213 (2010)) in μp 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 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
∞
= 10 973 731.568 160 (16) m
-1
and the rms charge radius of the deuteron r
d
= 2.128 09 (31) fm.
The Lamb shift in muonic hydrogen Pohl, Randolf; Antognini, Aldo; Nez, Francois ...
Canadian journal of physics,
01/2011, Letnik:
89, Številka:
1
Journal Article
Recenzirano
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 μp 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.sub.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.sub.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.sub.∞ = 10973 731.568160(16) m.sup.-1 and the rms charge radius of the deuteron r.sub.d = 2.128 09 (31) fm.
Noise sensitivity of an atomic velocity sensor Cladé, Pierre; Guellati-Khélifa, Saïda; Schwob, Catherine ...
The European physical journal. D, Atomic, molecular, and optical physics,
03/2005, Letnik:
33
Journal Article
Recenzirano
Odprti dostop
We use Bloch oscillations to accelerate coherently Rubidium atoms. The variation of the velocity induced by this acceleration is an integer number times the recoil velocity due to the absorption of ...one photon. The measurement of the velocity variation is achieved using two velocity selective Raman pi-pulses: the first pulse transfers atoms from the hyperfine state 5S1/2 |F=2, mF=0> to 5S1/2, |F=1, mF = 0> into a narrow velocity class. After the acceleration of this selected atomic slice, we apply the second Raman pulse to bring the resonant atoms back to the initial state 5S1/2, |F=2, mF = 0>. The populations in (F=1 and F=2) are measured separately by using a one-dimensional time-of-flight technique. To plot the final velocity distribution we repeat this procedure by scanning the Raman beam frequency of the second pulse. This two pi-pulses system constitutes then a velocity sensor. Any noise in the relative phase shift of the Raman beams induces an error in the measured velocity. In this paper we present a theoretical and an experimental analysis of this velocity sensor, which take into account the phase fluctuations during the Raman pulses.
By means of pulsed laser spectroscopy applied to muonic hydrogen (μ− p) we have measured the 2S F=1 1/2−2PF=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 μ 4He+and μ 3He+2S-2P splittings. The alpha and triton charge radii are extracted from these measurements with relative accuracies of few 10−4. 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.
We calculate the cross-damping frequency shift of a laser-induced two-photon transition monitored through decay fluorescence, by adapting the analogy with Raman scattering developed by Amaro et al. ...P. Amaro et al., PRA 92, 022514 (2015). We apply this method to estimate the frequency shift of the 1S-3S transition in hydrogen and deuterium. Taking into account our experimental conditions, we find a frequency shift of less than 1 kHz, that is smaller than our current statistical uncertainty.
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