Doppler effect in resonant excitation of CF3SF5 probed by Auger electron spectroscopy

Atomic-like Auger electron emission was observed in resonant excitation of F1s electron into the σCSF* molecular orbital of CF3SF5. This finding means that an SF bond forming the CSF linear skeleton in the ground state dissociates in the order of femto-seconds. The Auger electron emitted from the F atom showed a Doppler shift by using angle-resolved photoelectron spectroscopy. Asymmetry parameter for the leaving F atom relative to the linearly polarized electric vector was deduced to be β = 1.9 at high photon energy of 688.7 eV and a value of β = 1.1 by detuning the photon energy down to 686.8 eV. The variation of β on the exciting energies projects a profile that an axial recoil approximation effectively works for the ultrafast SF dissociation when the F1s−1σCSF* state is generated at high energy level on the σCSF* potential curve but retardation effects between the F and CF3SF4 fragments become noticeable at low energy level where kinetic energy of the F atom gets smaller.