2nd/3rd Year Undergraduate Experiments in Physical Chemistry
7.12 Photoelectron Spectroscopy
Introduction ||
Location ||
Safety ||
Instructions
The energy required to ionize a molecule is the difference between its total energy and that of its positive ion. This energy is a small difference (ca. 10eV) between two large (>500 eV) quantities and often the correlation between experimental and theoretical data is poor. A better correlation exists with the energy of the orbital occupied by the electron to be removed. Thus if we determine the ionization energies of a molecule using Photoelectron Spectroscopy as in this experiment, we in effect measure directly the molecular electron energy levels. Experimentally, we determine the energy spectrum of the photoelectrons ejected by photons whose energy is much larger than the ionization energies. We are thus examining processes occurring in the ionization continua. In this experiment you will use a photoelectron spectrometer to measure the PES of several gases, which have spectra that are both interesting and instructive. (A more extensive introduction is provided with the experiment script.)
Lower Teaching Laboratory.
Health and safety data for the chemicals to be used in this experiment are available through the links below.
Instructions for this experiment are available for reference in a folder in the Lower Teaching Laboratory. You may obtain a personal copy from the technician in that laboratory, or download a copy in pdf format (12 pages, pdf, 158k, updated Sep 10, 2003).
Updated September 11, 2003.