EXCITED STATES OF THE DIATOMIC MOLECULE CrHe
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Publisher:Ohio State University
Chromium (Cr) atoms embedded in superfluid helium nanodroplets (He$_N$) have been investigated by laser induced fluorescence, beam depletion and resonant two-photon ionization spectroscopy in current experiments at our institute. Cr is found to reside inside the He$_N$ in the a$^7$S ground state. Two electronically excited states, z$^7$P and y$^7$P, are involved in a photoinduced ejection process which allowed us to study Fano resonances in the photoionisation spectra. The need for a better understanding of the experimental observations triggered a theoretical approach towards the computation of electronically excited states via high-level methods of computational chemistry. Two well-established, wave function-based methods, CASSCF and MRCI, are combined to calculate the potential energy curves for the three states involved. The character of the two excited states z$^7$P and y$^7$P turns out to be significantly different. Theory predicts the ejection of the Cr atom in the case of an y$^7$P excitation as was observed experimentally. The quasi-inert helium environment is expected to weaken spin selection rules, allowing a coupling between different spin states especially during the ejection process. We therefore extend our theoretical analysis to the lowest state in the triplet- and quintet- manifold. Most of these alternative states show very weak bonding of only a few \wn.
Author Institution: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria