F 1s spectroscopy and ionic fragmentation of trifluoropropyne

Abstract

The F 1s excitation spectroscopy and ionic fragmentation of 3,3,3-trifluoro-1-propyne have been studied using synchrotron radiation and ion time-of-flight mass spectrometry. The total ion yield spectrum and photoionization branching ratios in the vicinity of the F 1s ionization threshold are reported. Core excited state calculations using the static exchange approximation are used to aid in the interpretation of the experimental results. The F 1s excitation spectrum consists of a number of broad overlapping bands below threshold, attributed to excitations to mixed σ*(C-F)/π*(C-C) molecular orbitals and unresolved Rydberg states, and a continuum shape resonance 12.5 eV above threshold. Ionic fragmentation following F 1s excitation or ionization results overwhelmingly in singly charged ionic fragments, primarily via cleavage of bonds to the fluorinated carbon atom adjacent to the core-excited atom.Key words: F 1s excitation, XANES, photoelectron-photoion coincidence, ionic fragmentation, static exchange approximation.