Physical Review A
An improved anisotropy measurement of the Lamb shift is obtained by means of a new method for the high-precision measurement of light intensities. The photon-counting techniques used in our previous work [Phys. Rev. A 20, 1299 (1979)] are replaced by the direct measurement of photoelectron currents with high-precision electrometers. Our new value for the Lamb shift in He+ is 14 041.91.5 MHz. This agrees with the earlier microwave resonance measurement of Lipworth and Novick [Phys. Rev. 108, 1434 (1957)], but lies clearly below the more recent measurement by Narasimham and Strombotne [Phys. Rev. A 4, 14 (1971)]. © 1987 The American Physical Society.
Patel, J.; Van Wijngaarden, A.; and Drake, Gordon W. F.. (1987). Improved anisotropy measurement of the Lamb shift in He+. Physical Review A, 36 (11), 5130-5137.