Jahn-Teller coupling and fragmentation after core-shell excitation in CF4investigated by partial-ion-yield spectroscopy

Abstract

We investigate fragmentation processes induced by core-level photoexcitation in CF 4 at both the carbon and fluorine K edges by means of partial-ion-yield spectroscopy. The molecule CF 4 is a textbook example of systems in which Jahn-Teller coupling strongly manifests itself in the photoabsorption spectrum. Spectral features related to Jahn-Teller and quasi-Jahn-Teller splitting are observed, and important differences in the fragmentation pathways are revealed depending on the symmetries of the core-excited states. We interpret these experimental observations on the grounds of symmetry lowering from the T d to the C 3v point group as well as preferential orientation with respect to the polarization vector of the incident radiation.

Inner-shell photoionization and core-hole decay of Xe and XeF2

“…F 1s photoionization of several small molecules (SF 6 , SiF 4 , BF 3 , and CF 4 ) primarily produces singly-and doubly charged fragment ions. [78][79][80][81] This is consistent with a simple picture of F 1s photoionization followed by a single Auger decay step that produces low total charge states. With low total charge on the molecular ion, the kinetic energies of the fragment ions are smaller than for decays of Xe 3d holes.…”

Conformational and nuclear dynamics effects in molecular Auger spectra: fluorine core-hole decay in CF4

“…The photoabsorption spectrum of CF 4 at the fluorine K-edge is characterized by a below threshold resonance corresponding to an excitation into the 5t 2 anti-bonding orbital [30]. The cross-section above the ionization edge is almost structureless.…”

Ultrafast dynamics in C 1s core-excited CF4 revealed by two-dimensional resonant Auger spectroscopy

“…We can point out a series of changes between the resonant and non-resonant case. The first observation is that the three highest-kinetic-energy spectral features, labeled 1t 1 , 4t 2 , and 1e, 22 significant resonant enhancement. This is easily understood on the ground of the nature of the corresponding molecular orbitals: they are all mostly built of F 2p combinations with lone-pair character, and therefore they are not affected by the decay of the resonant state in which the core hole is located on the carbon atom.…”

“…In a previous work by some 0021 of us, partial positive and negative ion yield around both C 1s and F 1s ionization thresholds was used to characterize the dynamics following core-level excitation and ionization. 22 Photoabsorption data have been reported around the C 1s ionization threshold. 23 Resonant Auger decay spectra were shown in Ref.…”