## Fragmentation of valence electronic states of CHF2CF3+ studied by threshold photoelectron–photoion coincidence (TPEPICO) techniques in the photon energy range 12–25 eV

### Abstract

Vacuum ultraviolet synchrotron radiation and threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy have been used to study the decay dynamics of the valence electronic states of CHF$$_2$$CF$$_3^+$$. The threshold photoelectron spectrum (TPES) and ion yield curves of the observed fragments have been recorded in the photon energy range 12-25 eV. Electrons and ions are detected by threshold electron analysis and time-of-flight mass spectrometry, respectively. Using a combination of the measured TPES and ab initio molecular orbital calculations, we conclude that the CHF$$_2$$CF$$_3^+$$ cation adopts a staggered C$$_s$$ geometry, the $$X$$~ $$^2$$A' ground state being formed by electron removal from the 18a' -bonding orbital of CHF$$_2$$CF$$_3$$. Upon ionisation, large geometry changes and broad spectral bands are both predicted and observed. The next outer-valence orbitals of CHF$$_2$$CF$$_3$$, 17a' and 11a", are predominantly associated with fluorine 2p orbitals located on the CHF$$_2$$ group. Translational kinetic energy releases are determined from fixed-energy TPEPICO-TOF spectra. The ground state of CHF$$_2$$CF$$_3^+$$ dissociates through CC bond cleavage with a relatively small release of energy. By contrast the $$A$$~ and $$B$$~ states dissociate rapidly by an impulsive mechanism with a larger fractional release of energy to CHFCF$$_3^+$$ + F. Upper limits for the ionization threshold of CHF$$_2$$CF$$_3$$ (12.70 $$\pm$$ 0.05 eV) and the enthalpy of formation of CHFCF$$_3^+$$ at 298 K (299 $$\pm$$ 7 kJ mol-1, respectively) are determined

Topics: QD Chemistry
Year: 2002
DOI identifier: 10.1016/S0301-0104(02)00790-5
OAI identifier: oai:eprints.bham.ac.uk:682

### Suggested articles

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.