The MIV,Vspectra of⁶³Eu

The M IV and M V absorption spectra of Eu in the form of the oxide and fluoride have been studied in detail. The fluoride spectrum was similar to that reported by Zandy but two types of spectra were observed with the oxide absorbers. One was the same as the fluoride spectrum but the second type was shown to be due to partially reduced absorbers consisting of metallic Eu and Eu 2 O 3 . Evidence is presented and discussed which indicates that nearly all the M IV,V absorption is due to transitions of electrons into the incomplete 4f shell and that practically no `edge' absorption occurs.