Dichroism In Photoelectron Spectroscopy Research Articles

Resonant Circular Dichroism of Chiral Metal-Organic Complex

A sizable enhancement of the circular dichroism in photoelectron spectroscopy has been measured and computed for the metal complex Δ-cobalt(III) tris-acetylacetonate highest occupied molecular orbital state in the region of the Co 3p→3d Fano resonance. In the resonance the dichroism reaches the maximum value of 5% and even changes its sign as compared to the direct photoionization channel. We ascribe this enhancement to electron correlation processes, namely, with the coupling between discrete excitations and the continuum, which is correctly described in the time dependent density functional theory (TDDFT) framework. These findings open new physical aspects of photoelectron circular dichroism that now can be interpreted not only via the simple direct ionization, but also through more complex electron correlation processes.

Circular dichroism in photoelectron spectroscopy of free chiral molecules: Experiment and theory on methyl-oxirane

We report a joint experimental and theoretical study of circular dichroism in the valence photoelectron spectra of a free chiral molecule. The circular dichroism in photoelectron spectroscopy is measured at the magic angle for various valence states of $R(+)$ and $S(\ensuremath{-})$ methyl-oxirane enantiomers in the vapor phase. The maximum dichroism measured is about $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$. Experimental and theoretical results are in agreement. The ab initio calculation employs a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian.

Direct extraction of exchange splittings from magnetic X-ray dichroism in photoelectron spectroscopy

It will be demonstrated that core-level exchange splitting can be extracted directly from normalized difference curves in magnetic X-ray circular dichroism (MXCD) in angle-resolved photoelectron spectroscopy (PES). Although high resolution is a requirement for the method, this determination can be performed without resorting to time-consuming and difficult spectral simulations. For well-defined cases, it will be shown empirically that this method may also work for the analysis of magnetic X-ray linear dichroism (MXLD). Applying this approach, it will be possible to use MXCD and MXLD in PES for direct surface magnetometry with full elemental specificity.

Magnetic x-ray dichroism in the spectroscopy of ultrathin magnetic alloy films

The magnetic structure of nanoscale alloy films has been probed using the magnetic x-ray linear dichroism in photoelectron spectroscopy and magnetic x-ray circular dichroism in x-ray absorption spectroscopy. FeNi and CoFe epitaxial films were grown on Cu(001), in situ and using MBE techniques. Because soft x-rays were used to probe the 2p and 3p core levels, both elemental selectivity and magnetic sensitivity were achieved simultaneously. Correlation of these magnetic techniques with compositional and structural information will be done. Ultimately, from studies such as this a complete determination of the structure-property relationships will be achievable.

Magnetic x-ray linear dichroism in the photoelectron spectroscopy of ultrathin magnetic alloy films

The magnetic structure of nanoscale alloy films has been probed using the magnetic x-ray linear dichroism in photoelectron spectroscopy. FeNi and CoFe epitaxial films were grown on Cu(001), in situ and using molecular beam epitaxy techniques. The magnetic x-ray linear dichroism measurements were made at the Spectromicroscopy Facility of the Third Generation Advanced Light Source. Because soft x-rays were used to generate photoemission from the 3p core levels, both elemental selectivity and magnetic sensitivity were achieved simultaneously.