X‐ray photoelectron spectra of the U 4f levels in UF₄, UF₅ and UF₆

UF₆, UF₅ and UF₄ have been studied by X‐ray photoelectron spectroscopy. U 4f_7/2 binding energies for these compounds were observed to be 384.9, 383.4 and 382.3 eV, respectively. The corresponding U 4f_5/2 energies were 395.7, 394.2 and 393.2 eV. Solid UF₆ was formed by condensation of a molecular beam onto Ni and Cu substrates at −80° C. UF₄ was produced by reaction of the UF₆ beam at higher substrate temperatures (−30° C and 25 °C). UF₅ was produced at higher temperature and pressure by reaction of Cu and UF₆. In the X‐ray photoelectron spectroscopy vacuum chamber, the UF₅ converted slowly to UF₄, probably by disproportionation and loss of UF₆.