Fine Structure of Short-Lived States of Hydrogen by a Microwave-Optical Method. I

A radio-frequency determination of the fine structure of excited states of hydrogen atoms is described. In this method the atoms are excited by electron bombardment so that they emit radiation. Transitions among the fine structure levels are induced by a radio-frequency electric field and are detected by the consequent change in intensity of the emitted radiation. A detailed theory of the method is presented and the experimental apparatus is discussed and described. Some preliminary results for the $n=3\mathrm{}$ level of deuterium are: $\Delta E-\mathcal{S}=2934.5\mathrm{}\pm 10$ Mc/sec, $\mathcal{S}=316.3\mathrm{}\pm 10$ Mc/sec, where $\Delta E$ is the separation $3{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}-3\mathrm{}{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$, and $\mathcal{S}$ the separation $3{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-3\mathrm{}{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$; these results are in agreement with predictions of quantum electrodynamics.