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Publikace ÚTF

Resonances and Dissociative Electron Attachment in HNCO

Zawadzki, M., Čížek, M., Houfek,K., Čurík, R., Ferus, M., Civiš, S., Kočišek, J. and Fedor, J.

In a combined experimental and theoretical study, we probe the dissociative electron attachment in
isocyanic acid HNCO. The experimental absolute cross section for the NCO− fragment shows a sharp onset
and fine structures near the threshold. The autoionizing state responsible for the dissociative attachment
is found in both the R-matrix calculation and using analytic continuation in the coupling constant. The
involved A0 resonance has a mixed π=σ character along the dissociating bond and thus combines the
effects of nonzero electron angular momentum and dipole-supported states. This leads to unusual behavior
of its width at various geometries. Because the potential energy gradient of the autoionizing state points
essentially in the direction of the N─H bond, nuclear dynamics can be described by a one-dimensional
nonlocal model. The results agree with the experiment both quantitatively and qualitatively. The present
system may be a prototype for interpretation of the dissociative electron attachment process in a number of
other polyatomic systems.
journal:Phys. Rev. Lett.
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