Electron Attachment and Excitation Processes in Selected Carbonyl Compounds

Short‐lived negative ions were observed in urea (2.2 eV), acetone (1.6 eV), acetaldehyde (1.2 eV), acetophenone (0.95 eV), benzophenone (0.75 eV), and benzaldehyde (0.72 eV), using the SF₆ scavenger technique. The energy position of the peak of each resonance is given in parentheses. These resonances were assigned to the capture of an electron into the lowest vacant (π*) orbital of the carbonyl group. Hexafluoroacetone captures slow electrons $\text{(∼0\hspace{0.17em}}\mathrm{eV})$ into a long‐lived temporary negative ion state with an autodetachment lifetime of $\text{65± 10\hspace{0.17em}μ}\sec$ . Cl⁻ was observed through dissociative attachment of 0.5‐eV electrons to chloroacetone. Dissociative attachment to urea yielded CN⁻ and NCO⁻ around 2 eV and ${\mathrm{NH}}_2^{-}$ , NH⁻, OH⁻, and N₂H₃CO⁻ around 6 eV. Peaks in the threshold excitation spectra were observed in acetone at 4.15, 6.13, 7.5, and 8.1 eV; in acetaldehyde at 3.8, 6.35, and 6.62 eV; and in urea 6.1 and 8.4 eV.