Ultraviolet photoelectron spectroscopy

The ultraviolet photoelectron spectroscopy ( UPS ) is a method of analysis of the group of photoelectron spectroscopy ( PES). It is mainly used to determine the valence band structure of solids ( in solid-state often referred to as Valenzbandspektroskopie ), surfaces and adsorbates. Determined the density of states (english density of states, DOS). For this is the exciting energy of light ( see photoelectron spectroscopy) in the ultraviolet wavelength range and is therefore only able to trigger valence electrons. These energies are, of course, the XPS measurement also accessible only can (generally helium gas discharge lamps ), the kinetic energy of the photoelectrons as measured with extremely high accuracy by a suitable choice of the light source. With UPS also minimal energy differences of molecular orbitals or the physical environment can be resolved (eg, adsorption on surfaces) of spectroscopically molecule. Can be investigated is the chemical structure of bonds, adsorption mechanisms of substrates and vibrational energies of various molecular gases.

Radiation sources

For ultraviolet photoelectron spectroscopy radiation sources for the energy range of 10 up to 100 eV are required:

• Energy of the radiation or
• Resolution

Determination of the density of

There are three different methods by which either the so-called JDOS (Joint Density of States ), a combination of occupied and unoccupied states, the density of occupied states or the density of unoccupied states is determined. With He gas discharge lamps only JDOS can be measured as a variation of the photon energy is necessary for the other methods.