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The dependence of the photoelectric activity on the helicity of light is called circular dichroism in photoemission. Circular dichroism in photoemission on chiral molecules is closely related to circular dichroism in photoabsorption and was theoretically treated 20 years ago. This work provides the first experimental proof of circular dichroism in photoemission on chiral Compounds. A quantum mechanical treatment of the effect with special regard to symmetry arguments is given in the first chapter. It is shown that circular dichroism is highly sensitive to the experimental geometry. Totally unoriented Systems, e.g. molecules in the gas phase or in Solution or suspended particles, exhibit circular dichroism only if the photoemitters are chiral. Consequently, circular dichroism reverses its sign, when the handedness of the molecules is changed. Furthermore one has to distinguish between measurements where the photoelectrons are detected angle resolved or angle integrated. In the angle resolved case, circular dichroism already occurs in dipole approximation. By measurement of the angle integrated photocurrent, in contrast, circular dichroism can only be explained by second order terms. Compared to the leading dipole transition term, the second order terms scale with the ratio of radius of the light absorbing orbital to the wavelength of light. Using uvlight, a scaling factor below 1% is expected. Aerosol particles consisting of binaphthalene derivatives are used for the first exper¬ imental proof of circular dichroism in photoemission on chiral Compounds. A new apparatus is set up including a source for chiral aerosols and a photoemission Chamber, where the particles are charged by irradiation with right or left circularly polarized uv-light. The Charge of the particles is measured with a high sensitivity electrometer. This quantity is related to the total photoelectric activity. The measured asymmetries are found to be in the ränge of 2 %o. The uncertainty of the measurement is about 0.1%o. It is checked that the measured asymmetry reverses its sign when the generated particles consist of the mirror-isomer. This is a clear confirmation that the observed circular dichroism is due to the chirality of the molecules and not the result of an intrinsic asymmetry in the detection System. Further experiments have been carried out with particles consisting of amino acids, the basic units of the proteins. It is found that the photoelectric activity is highest for particles of amino acids containing aromatic side chains. Asymmetries close to 1%

Circular dichroism in the photoionization of chiral compounds