On the assignment of the carbon K-shell spectra of the methyl halides

Electron energy loss spectra of the methyl halides in the region of carbon K-shell excitation have been obtained at higher resolution than those previously reported. The existence of two electronic transitions between 288 and 290 eV in CH3F is demonstrated. This result conflicts with a recent SCF calculation which suggests that the σ* (C–F) level in CH3F is unbound and thus predicts the existence of only one electronic transition in this spectral region. Studies of the carbon K-shell spectra of CH3Br and CD3Br demonstrate the vibrational origin of some spectral features. These new results support our earlier tentative assignments for the carbon K-shell spectra of the methyl halides.