Experimental Evidence for Circular Dichroism in the Double Photoionization of Helium

Circular dichroism in the double photoionization of He by circularly polarized light has been observed in an angle resolved coincidence experiment at 93.5 eV photon energy. The use of a transmission multilayer, which acts as a quarter-wave plate for the linearly polarized incident light, together with time-of-flight spectrometers, which enable simultaneous detection of all electron pairs, has made the measurements possible. The results show strong dependence of the dichroism on the relative emission angles and the energy sharing between the ejected electrons in good agreement with our numerical calculations. {copyright} {ital 1996 The American Physical Society.}