Precision Measurement of the1s2pP32

Abstract

Using Doppler-tuned fast-beam laser spectroscopy with co-and counterpropagating beams we have measured the three hyperfine components of the 1s2p 3 P 2 -3 P 1 fine structure interval in 19 F 71 . Our result for the centroid is 957.6679͑10͒ cm 21 . Allowing for the hyperfine interaction the "pure" fine structure interval is determined to be 957.8730͑12͒ cm 21 . This result tests O͑a 7 m e c 2 ͒ quantum electrodynamic corrections to high precision calculations which will be used to obtain a new value for the fine structure constant from the fine structure of helium. [S0031-9007 (99)09157-7] PACS numbers: 32.10.Fn, 06.20.JrThe fine structure constant, a, is the fundamental constant which expresses the elementary charge in dimensionless form and hence plays a crucial role in unifying an enormous range of physical phenomena [1]. There is now a program to obtain a new value for a from comparison of theory and experiment for the 1s2p 3 P J2J 0 fine structure of atomic helium. Drake and co-workers, using matrix elements of operators derived from the Bethe-Salpeter equation, evaluated with high-precision nonrelativistic wave functions, aim to complete calculations to order a 5 a.u. (or a 7 m e c 2 ) [2-4]. Independent calculations of the effective operators are also being carried out by Pachucki [5]. This is expected to result in a theoretical value for the larger, approximately 29.6 GHz, J 0 1 interval in helium to better than 61 kHz. Combined with measurements aimed at exceeding this precision [6-9], this should yield a value for a at the 16 ppb (parts per 10 9 ) level. This would be of interest for comparison with the result obtained from QED theory and experiment for the electron magnetic moment, and with results obtained from the various other phenomena reviewed in Ref. [1].Compared to other methods dependent on QED theory for obtaining a, helium fine structure has an advantage in that the theory, in particular, the evaluation of the complex higher-order relativistic and QED corrections, FIG. 1. Schematic of the experimental arrangement. G is a diffraction grating, W is a window, L is a lens, M1, M2 are mirrors, EM1, EM2 are electromagnets, PM is a permanent magnet, and PC is a proportional counter.can be independently tested. This is because there are two 2 3 P fine structure intervals and because the same methods used for helium can be used to calculate fine structure in moderate Z heliumlike ions where the relative magnitudes of these higher-order terms are larger. Hence fine structure measurements in moderate Z heliumlike ions [10-15], even though less precise than measurements in helium, can provide sensitive tests of the theory. Here we report a measurement of the three hyperfine components of the 19 F 71 1s2p 3 P 2 -3 P 1 fine structure interval, obtained by directly inducing the M1 transitions using a CO 2 laser, in a fast, foil stripped fluorine ion beam. A novel Doppler shift cancellation technique was used which measures products of the transition energies in pairs. Our result, with a precision of 61 ppm ...

Measurement of the1s2s1S

“…The peak signal height is consistent with the estimated transition probability. The observed resonance width, equivalent to 1.03 6 0.3 cm 21 FWHM, is consistent with the (Lorentzian) natural width of 0.834 cm 21 , the estimated transition probability, which leads to power broadening (due to depopulation of 1s2s 1 S 0 ) of approximately 10%, and a Gaussian contribution of 0.3 cm 21 , due to an estimated beam energy spread after the foil of 50 keV FWHM [34][35][36].…”

Fine structure of helium and light helium-like ionsThis 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.

“…These are the measurement of ν 01 in helium-like nitrogen by Thompson at al. [31] and that of ν 12 in helium-like fluorine by Myers et al [32]. Good agreement of the present theory with these experimental results suggests that the theoretical errors (i.e., the uncalculated higher-order effects) were reasonably estimated.…”

Towards numerical implementation of the relativistically covariant many-body perturbation theoryThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at University of Windsor, Windsor, Ontario, Canada on 21–26 July 2008.

“…Accurate results for the fine structure have also been achieved for heavier ions, like F +7 and Si +12 [6,7]. For Si +12 , the closest theoretical results come from combining RMBPT calculations by Plante et al [8] with QED calculations by Drake [9], which also deviate significantly from the experimental value.…”