X-ray absorption spectroscopy of mass-selected transition metal clusters using a cyclotron ion trap: An experimental setup for measuring XMCD spectra of free clusters

摘要

A Fourier-Transform-Ion-Cyclotron-Resonance mass spectrometer has been installed at the BESSY II storage ring. This unique setup enables to record soft X-ray absorption and magnetic circular dichroism spectra (XMCD) of mass-selected clusters in the photon energy range 200-1200 eV. The photoabsorption signal is obtained by recording the fragmentation pattern as produced after X-ray absorption and subsequent Auger decay of the core-excited parent cluster ion. The experimental setup and first X-ray absorption spectra on V13+ and Nb13+ are discussed. The feasibility of recording X-ray induced XMCD spectra is demonstrated for Co 22+. Improvements that allow for quantitative determination of spin and orbital momenta in the future are briefly outlined.