Radiative Mean-Life Measurements of Some Atomic-Hydrogen Excited States Using Beam-Foil Excitation

The beam-foil excitation method has been used to measure the radiative mean lives of the $2p$ and $3p$ states of atomic hydrogen. The results obtained were (1.60±{}0.01)×{}10^-9 sec and (5.5±{}0.2)×{}10^-9 sec, respectively. A study of the results of this experiment has led to the following conclusions: (a) the Lyman-α decay curves are best fitted by the sum of two exponential terms whose characteristic decay times correspond to spontaneous decay of the $2p$ state and repopulation of this state by higher states, (b) the shapes of the Lyman-α decay curves vary with foil thickness, and (c) the ion energy loss in the foils used in this experiment changes with the age of the foil. A review of previous measurements on atomic-hydrogen radiative mean lives is also made and compared with theory.