Low-Energy Electron-Reflection Spectrometry for Thin Films of Aromatic and Aliphatic Molecules at 77°K

Abstract

Low‐energy electron‐reflection (LEER) spectra have been measured for thin films of pyridine, mesitylene, toluene, aniline, 1‐hexene, cyclohexene, 2‐methylpentane, and cyclohexane at 77°K. Differential plots show clearly defined peaks which appear to correspond to near‐resonant energy losses. For the aromatic molecules these peaks are matched by spectroscopically measured electronic energy levels, including both singlets and triplets. The aliphatic molecules show low‐lying bands in the LEER spectra, indicating states which have not been proposed previously and do not correlate with spectroscopically measured energy levels. For 1‐hexene the two lowest peaks occur at ∼ 3.1 and ∼ 4.6 eV; for cyclohexene at 3.0 and 4.7 eV; for 2‐methylpentane at 3.9 and 4.9 eV; and for cyclohexane at 3.9 and 4.8 eV.