H. A. Bethe and E. E. Salpeter, Quantumn Mechanics of One and Two Electron Atomns (Academic Press, Inc., New York, 1957).
L. R. Maxwell, Phys. Rev. 38, 1664 (1931).
Note added in proof. We have recently become aware of another measurement of the lifetime of the 4S state giving the result (1.36±0.20)×10-8 sec. [L. L. Hatfield, thesis, University of Arkansas (1967)].
L. Kay, Phys. Letters 5, 36 (1963); Proc. Phys. Soc. (London) 85, 163 (1965).
S. Bashkin, Nucl. Instr. & Methods 28, 88 (1964); S. Bashkin, L. Heroux, and J. Shaw, Phys. Letters 13, 229 (1964); A. S. Goodman and D. T. Donahue, Phys. Rev. 141, 1 (1966); W. S. Bickel and S. Bashkin, Phys. Letters 20, 488 (1966); S. Bashkin, D. Fink, P. R. Malmberg, A. B. Meinel, and S. G. Tilford, J. Opt. Soc. Am. 56, 1064 (1966); W. S. Bickel and A. S. Goodman, Phys. Rev. 148, 1 (1966).
The foils are obtained from the Yissum Research and Development Company, Hebrew University, Jerusalem, Israel.
Survey work using an Astro Mechanics f/2 Meinel spectrograph, borrowed from the U. S. A. F. Aerospace Research Laboratory, had indicated that the spectral lines studied could be sufficiently isolated by moderately narrow-band interference filters (with the half-width of the passband on the order of 70 Å).
Straight-forward photon-counting techniques would have yielded a pulse rate too rapid for certain of the scalers available to us and for a projected on-line computerized data-acquisition and analysis system.
The uniqueness of the minimum in Σ R2, which we find, can be questioned. To the best of our knowledge, there is no proof that any fitting procedure yields a unique fit to a sum of exponentials. The initial values of the lifetime used in our iterative program differed from run to run and were within about ±30% of the calculated values.
F. L. Roesler and J. E. Mack, Phys. Rev. 135, 57 (1964).
G. F. Drukarev, The Theory of Electron-Atom Collisions (Academic Press Inc., New York, 1965).
S. Bashkin, W. S. Bickel, D. Fink, and R. K. Wangsness, Phys. Rev. Letters 15, 284 (1965).
See, e.g., R. T. Robiscoe and B. L. Cousens, Phys. Rev. Letters 17, 69 (1966) and references therein.
Another variation of the high-energy atomic-beam technique, which makes use of Stark mixing in a static electric field, has been used by C. Y. Fan, M. Garcia-Munoz, and I. A. Sellin, Phys. Rev. Letters 15, 15 (1965), to measure the Lamb shift in Li III.