Journal of Physics B: Atomic and Molecular Physics
The strong field-induced quantum beats observed in beam-foil studies of Ly- alpha radiation are obtained in a conventional metastable-hydrogen quenching experiment. The phase relation between the Stark shifted 2s 1/2- 2p 1/2 Lamb-shift oscillations and the much more rapid 2s 1-2p 3/2 fine-structure oscillations depends on the detailed way in which the quenching field is switched on. Apart from a phaseshift, the results agree with a non-perturbative theoretical calculation which assumes that the field is applied suddenly. Various frequency components of the time-dependent radiation intensity are identified with specific hyperfine transitions or groups of transitions. No adjustable parameters are used for the initial state amplitudes.
Van Wijngaarden, A.; Goh, E; Drake, Gordon W. F.; and Farago, P. S.. (1976). Quantum beats in the electric-field quenching of metastable hydrogen. Journal of Physics B: Atomic and Molecular Physics, 9 (12), 2017-2025.