Stimulated Emission in the Hydrogen Maser and the H Spin-Exchange Cross Section

Experiments are described in which the phenomenon of stimulated emission with a delayed maximum of power is observed in a hydrogen maser and is studied in some detail. The results are coupled to measurements of relaxation rates made through a pulse technique in which the hydrogen beam is modulated. A solution of the rate equations describing the phenomenon for a two-level model is obtained on an analog computer and is compared with the experimental data. From the comparison, we conclude that the phenomenon is explained by the assumed theoretical model. It is found also that the published values of the spin-exchange cross section of hydrogen are consistent with our experimental data.