Study on molecular dissociation governed by femtoseconds dynamics of core-excited molecules

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1.We have measured resonant photoemission spectra of the CF_4, CH_3F, and SF_6 molecules after photoexcitation of the F 1s core electron to the lowest unoccupied molecular orbital and found the Auger electron emission from the F atomic fragment. The Doppler energy shifts of the F atomic Auger lines provide experimental evidence that the ultrafast dissociation takes place, where one C-F or S-F bond is elongated along the electric vector of the light and ruptured.2.Replacing the CCD camera of the electron detector in the electron energy analyser (Gammadata-Scienta SES2002) to the delay-line detector and combining it with the ion momentum spectrometer, we have constructed the Auger electron -ion momentum coincidence spectrometer.3.Using the Auger electron -ion momentum coincidence spectrometer, we have investigated ultrafast dissociation after the core excitation of CF_4, CH_3F, and SF_6 molecules and found the following.(1)Kinetic energy of the F ion is less than the half of the available excess energy and the rest goes to the vibrational excitation and further fragmentation of the molecular fragment.(2)Ultrafast dissociation also takes place after C 1s excitation of CH_3F and produces the CH^+ ion.(3)The F 1s atomic Auger electron is scattered by the CF_3 fragment.(4)Before the dissociation is complete, electron migration takes place from the CH_3 fragment to the F atomic fragment in which the Atomic-like Auger decay takes place.