Inner shell electron energy loss spectra of the methyl amines and ammonia

Abstract

Electron energy loss Spectroscopy has been used to obtain the inner shell excitation spectra of the methyl amines CH 3NH 2, (CH 3) 2NH and (CH 3) 3N for both the N 1 s and C 1 s regions. A spectrum of the N 1 s region of NH 3 is also presented at higher resolution than previously published data. The C l s spectra are all very similar and the discrete portions may be assigned to Rydberg transitions. However, features attributable to a σ * shape resonance are observed just above the N 1 s and C l s ionization edges. The NH 3 spectrum is ascribed to Rydberg transitions. The N 1 s spectra of the methyl amines, however, become increasingly dominated by a σ* resonance in the continuum with increased methylation. The features in the inner-shell spectra are compared with the reported valence-shell optical absorption spectra and support the Rydberg assignment. The inner-shell spectra of (CH 3) 3N and NH 3 are also compared with previously published inner shell electron energy loss spectra of NF 3 and the third row phosphorus analogues PF 3,P(CH 3) 3andPH 3.