Electronic spectra of isoelectronic amides, acids, and acyl fluorides

The first four bands in the gas-phase spectra of amides, carboxylic acids, and acyl fluorides are thought to be n→π*, n→3s Rydberg, π→π*, and n→3s Rydberg excitations. That the second and fourth bands are Rydberg, whereas the first and third are valence shell is demonstrated in a comparison of gas-phase and condensed-phase absorption and circular dichroism spectra. All-electron, SCF Gaussian orbital calculations are also presented which qualitatively explain the trends in the spectra of HCOX molecules, and predict several quantities of interest, such as upper-state dipole moments and magnetic transition moments, which have not been measured as yet.