Chemical bonding information from photoelectron spectroscopy.

High-resolution measurements of photoelectrons produced by x-rays in compounds of iodine and europium have revealed chemical shifts in the core-level energies, from which chemical bonding information can be obtained. The observed shifts, 0.8 electron volt per unit change in oxidation number in iodine and 9.6 electron volts in europium, are discussed in terms of two theoretical models.