IONIZATION POTENTIALS AND LAMB SHIFTS OF THE GROUND STATES OF $sup 4$He AND $sup 3$He
Journal Article
·
· Proc. Roy. Soc. (London)
In order to obtain an experimental value for the Lamb shift of the ground state of helium, it is necessary to determine a very precise value for the ionization potential. For this purpose the wavelengths of the far ultra-violet lines 584.3 (1/sup 1/S-2/sup 2/P/sub 1/), 537.0 (1/sup 1/S-3/sup 1/ P), and 591.4A (1/sup 1/S-2/sup 3/P/sub 1/) of He/sup 4/ have been redetermined with much improved accuracy and those of He/sup 3/ have been measured for the first time. The standards used were lines of C/sup +/ and A/sup +/ in the region 610 to 520A which were derived by means or the combination principle from lines at longer wavelengths. The final results for the wavelengths of the He/sup 4/ lines are 584.3339, 537.0293, and 591.4121A with an estimated accuracy of plus or minus 0.0005A. For He/sup 3/ the corresponding figures, obtained by adding the measured shifts to the He/sup 4/ wavelengths, are 584.3640, states of these lines relative to the ionization limit have been redetermined by a new measurement of the Bergruan series 3/sup 3/D-n/sup 3/F, of the intercombination lines 2/sup 3/P- 3/sup 1/D and 2/sup 1/P-3/sup 3/D and a remeasurement of the near ultra-violet 2/ sup 1/.P -n/sup 1/D and 2/sup 3/P -n/sup 3/D series. Combining these results with those of the far ultra-violet lines the following values for the ionization potentials of He/sup 4/ and He/sup 3/ are obtained: I.P.(He/sup 4/) = 198310.82 plus or minus 0.15 cm/sup -1/ I.P.(He/sup 3/) = 198300.32 plus or minus 0.15 cm/sup -1/. The isotope shift of the ground state, 10.50 plus or minus 0.05 cm/ sup -1/, agrees closely with the theoretical prediction. Experimental values for the Lamb shift are obtained by comparing the observed ionization potentials with those obtained from the Dirac theory not including quantum electrodyamic effects. Using Kinoshlta's 39-parameter value, one finds a Lamb shift of -0.7/sub 9/ and - 0.8/sub 2/ plus or minus 0.15 cm/sup -1/ for He/sup 4/ and He/su p 3/ respectively. STAAdded in proof: Using Pekerts's 203parameter value one finds - 1.1/sub 9/ and -1.2/sub 3/ cm/sup -1/, respectively.! The value predicted by Kabir, Salpeter & Sucher is -1.32 plus or minus 0.2 cm/sup -1/. (auth)
- Research Organization:
- National Research Council, Ottawa
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-13-002361
- OSTI ID:
- 4316277
- Journal Information:
- Proc. Roy. Soc. (London), Journal Name: Proc. Roy. Soc. (London) Vol. Vol: A248
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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