This contribution reports on the chemical, vibrational spectroscopic, and infrared multiphoton photochemical properties of uranium hexamethoxide, U(OCH3)6, a prototype molecule for laser-induced uranium isotope separation with a carbon dioxide laser. Uranium hexamethoxide can be prepared from UC14 by conversion to Li2U(OCH3)6, followed by oxidation with lead tetraacetate. Vapor pressure studies on U(OCH3)6 indicate that ΔHsub° = 23 ± 3 kcal/mol and ΔSsub° = 76 ± 4 eu; at 33 °C, the vapor pressure is 17 mtorr. The vibrational spectra of U(16OCH3)6 and U(18OCH3)6 have been assigned by using infrared and laser Raman data. Under idealized Oh symmetry, the U(16OCH3)6 U-O stretching fundamentals are assigned at 505.0 (A1g), 464.8 (T1u), and 414.0 cm-1 (Eg). Tentative assignments are also made for several of the overtone and combination transitions evidence for possible lowering of the symmetry is presented. In gas-phase infrared photochemical experiments, the predominant U(OCH3)6 photoproducts isolated are U(OCH3)5, methanol, and formaldehyde. These are suggestive of multiphoton U-O bond homolysis to produce uranium pentamethoxide and methoxy radicals. The enrichment of unreacted U(OCH3)6 in 235U is maximum at ca. 927 cm-1 (near what may be a U-O stretching overtone transition) and exhibits both a low fluence threshold and diminution at high fluence.
ASJC Scopus subject areas
- Colloid and Surface Chemistry