Electron Stimulated Desorption (ESD)
Isothermal ESD of the multilayers and monolayer of reactants on the Mo(110) surface is carried out to determine the products of electron irradiation. The electron beam used in our experiments is generated using the same UTI Model 100C quadrupole mass spectrometer used for detection. Electrons emitted from the mass spectrometer filament are accelerated to an energy of 55 eV (Figure 4). The electron energy can be modified by biasing the crystal. For example, a crystal bias of -50V will result in an electron energy of just 5 eV while biasing the crystal to +95V will produce 150 eV electrons.
These ESD experiments are performed by dosing the reactant onto the Mo(110) crystal at 100 K, monitoring the mass spectrometer signal with the crystal rotated away from the mass spectrometer, and then rotating the crystal into alignment with the mass spectrometer while noting the time at which alignment occurred. The data produced is then the mass spectrometer signal as a function of time. Similar to TPRS, the area under the desorption peak is proportional to the amount of that molecule desorbing during electron-irradiation.
Post-Irradiation Temperature Programmed Reaction Spectroscopy (TPRS)
Post-irradiation TPRS experiments are TPRS experiments carried out after isothermal ESD experiments. Their purpose is to characterize what is left behind after electron bombardment. For example, products may have been formed during isothermal ESD but not been ejected into the gas phase. After isothermal ESD experiments, standard TPRS procedures for heating and detection are followed.