MEMORY EFFECTS IN MOLECULAR FRAGMENTATION INDUCED BY SITE-SPECIFIC CORE EXCITATION USING A REFLECTRON TIME-OF-FLIGHT MASS-SPECTROMETER

Bond-selective fragmentation of the molecules CF2 = CH2 and CF3-CH3 is observed for site-specific C(1s) excitation. Excitation at either the fluorinated or hydrogenated C atom of CF2 = CH2 and CF3-CH3 shows that the molecule memorizes the initial site of energy deposition, hence a chemical "memory effect". To follow the site-specific fragmentation channels, we employ a new "zero kinetic energy (ZEKE)" photoelectron-photoion coincidence technique using monochromatized X-ray synchrotron radiation from BESSY. The detection of ZEKE electrons serves to select the specific excitation of a carbon atom within the molecule. The fragmentation channels were assigned with high mass resolution by using a reflection time-of-flight mass spectrometer.