Measurement of the ratio of the 2s to the 2p populations for beam-foil excited hydrogen

Ratios N2s/N3p of 2s to 3p populations in hydrogen atoms formed by the passage of protons through carbon foils have been measured using the beam-foil-laser excitation method reported very recently. No dependence of N2s/N3p on the incident proton energy Ep, in the 100-300 keV energy range analysed, is observed. From the ratio N3p/N2p of 3p to 2p beam-foil populations in hydrogen reported previously (N3p/N2p independent of Ep for Ep>100 keV) and the ratios N2s/N3p measured in the present work, a mean value of N2s/N2p equal to 0.61±0.04 is deduced. These results are compared with available experimental data. (orig.)