Orientation effect on photo-fragmentation and ion-desorption from the top most layers of molecular solids

Using a newly developed rotatable-time-of-flight mass spectrometer (TOF-MS) and polarized synchrotron radiation, we have investigated orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids. Polarization-angle dependencies electron- and ion-NEXAFS of a condensed layer of partially deuterated formamide (HCOND2) are reported. A marked orientation effect was observed for enhanced H+-yields following C 1s→σ∗C–H core-resonance. This effect was attributed to the existence of direct photodissociation as well as to the change of charge-neutralization probability. The product yields of some fragments, however, showed no polarization dependence especially when dissociation sites were far from core-excited atoms. This is the case for N–D breaking and D+-desorption following C 1s→σ∗N–D resonance. It suggests that higher Rydberg states with plural symmetries are mixed.