Circular dichroism in the photoelectron angular distribution of 2-amino-1-propanol and 1-amino-2-propanol

Natural circular dichroism in angle resolved photoemission with circular polarised light in the VUV - soft X-ray range is a promising technique in characterising the electronic properties of molecules, because the measured dichroic signal is one order of magnitude grater in respect to the absorption case [1]. Using circularly polarised synchrotron radiation source it is possible to couple the information of the molecular electronic states with the chiral properties of the molecule. In particular in previous works we measured the circular dichroism in the photoelectron angular distribution (CDAD) in constant initial state mode in the case of two ring molecules: the methyl- oxirane [2,3] and the 3-hydroxy tetrahydrofurane [4]. For the first time we have measured the CDAD in constant initial state mode in the case of two linear chiral molecules: alaninol (2-amino-1-propanol) and isopropanolamine (1-amino-2- propanol). The presence of dichroism also in quasi-symmetrical states indicates that the effect is related to the final state chiral character. The inversion of the two functional groups (-OH and -NH2) has produced interesting and not straightforward results about the interpretation of the geometrical and electronical contribution to the dichroic signal. The possible way to individuate a common path in the CDAD effect is a systematic theoretical and experimental study over family of molecules that share similar structure and functional groups. Circular dichroism in the angular distribution of valence photoelectrons emitted from randomly oriented alaninol and isopropanolamine enantiomers has been observed in gas-phase experiments using circularly polarized synchrotron VUV light. The measurements have been performed at several photon energy (25.1, 22.5, 20.5, 18.4, 16.6 eV) to study, for the first eleven valence states, the trend of the dichroism as a function of the kinetic energy of the photoelectrons. The present study could be very useful to explain the dependence of the dichroism from the electronic and structural properties of common functional groups as -OH and -NH2.