High Resolution - and Single Photon Electron Spectroscopy Using Hemispherical Electron Spectrometer with Positive-Sensitive Detection

The design and construction of a large-radius, hemispherical-geometry electron spectrometer is described. The spectrometer employs a position-sensitive microchannel detector with position decoding accomplished by the rise -time method. Either a high-energy ultraviolet lamp, or a pulsed, dye-laser are used to photoionize samples. Single (PES) and multiple photon (MPI:PES) ionization photoelectron spectroscopy of triethylamine (TEA) was studied. The adiabatic ionization potential of TEA was accurately determined using both single (7.47 +/- 0.04 eV) and multiphoton (7.53 +/- 0.10 eV) ionization photoelectron spectroscopy. Although excitation to both the S_1 and S_2 states can occur, multiphoton ionization always occurs out of the S_1 state. When dissociation of the cation occurs, the photoelectron energy distribution similarly reflects this partitioning. Bromochlorofluoromethane was also studied. By using a supersonic expansion to cool the gaseous sample, it was possible to discern and assign vibrational structure of several of the halogen photoelectron peaks. In addition, the adiabatic and vertical ionization potentials were found to be 10.95 +/- 0.05 eV and 11.28 +/- 0.02 eV, respectively.