On the Theory of Electron—Photon Coincidence Experiments

J. H. Macek, D. H. Jaecks

Robert S. Shankland

A test has been made of the photon theory of the scattering of high frequency radiation. The pairs of scattered photons and recoil electrons predicted by this theory have been looked for by means of specially designed Geiger-M\"uller counters. Coincident discharges in the electron and photon counters were recorded by means of a vacuum tube amplifying and adding circuit. The scatterers used were air, aluminum, beryllium, filter paper and paraffin. The radiation was the gamma-rays from radium C. Experiments were performed with the counters set at various angles, some where the photon theory predicts coincidences, and others where coincidences should not be expected. The experiments uniformly gave fewer coincidences in the correct positions than were expected, and those observed could in every case be accounted for as chance coincidences due to the finite resolving time of the apparatus. It has not been found possible to bring the results of these experiments into accord with the photon theory of scattering. The wave-mechanical theory of the scattering process has not yet been extended to include the gamma-ray region so that it is impossible to compare this theory with the present experiments. Unless it is shown that the two theories disagree in the gamma-ray region it does not seem possible to reconcile the present experiment with the Bothe-Geiger and Compton-Simon experiments.

Dennis J. Chornay

Liu Yi-Bao, Pang Wen-Ning, Ding Hai-Bing +2 more

Based on the general theory of the electron-photon coincidence experiment, the S tokes parameters of an excited atomic state were calculated with the distorted w ave Born approximation. According to the correlation between experiment and theo ry, the distribution of electron clouds in an excited atomic state can be descri bed by their orientation and alignment parameters. The values obtained are in g reement with the results of the experiments.

Klaus Bartschat, Karl Blum, G F Hanne +1 more

The authors present a theory of electron-photon coincidence experiments with polarised electrons, taking spin-orbit coupling effects during the excitation into account. The influence of the initial polarisation vector on the angular distribution and polarisation of the emitted photons is discussed in detail. As an explicit example the excitation process 1 S 0 to 3 P 1 in mercury is considered. Finally, the results are specialised to experiments where the scattered electrons are not observed. Using symmetry arguments and deriving additional selection rules they relate the degree of light polarisation to the initial polarisation. Two experimental results are presented.

Helmut Schwarz