Abstract

Recent advances in theory and experiment in the helium atom have elevated its importance as a laboratory for the study of fundamental interactions. Precise wavelength metrology is now crucial in tests of both one-and two-electron atoms. Wavelength measurements of lasers tuned to hydrogen resonances yield the Rydberg constant, which sets the scale of atomic energy levels, to a precision of 2-3 parts in 10¹¹, and an accuracy of 1.6 parts in 10¹⁰, limited by the realization of the meter. Measurements of transitions from the ground state of hydrogen test theory precisely by determining its Limb shift.

© 1992 Optical Society of America