Determination of Molecular Excitation Potentials by Electron Impact. An Anomaly in the N2 Spectrum

Abstract

An improved monochromator is described which provides an electron beam sufficiently homogeneous in energy so that peak widths range from 0.28 V at 400‐V kinetic energy to 0.13 V at 150‐V kinetic energy. Using this device excitation potentials have been determined for CO₂ and N₂. The highest peak in the spectrum of N₂ occurs at an excitation potential of 12.93 V while the most intense transition in the ultraviolet absorption spectrum, according to Huffman, Tanaka, and Larrabee, occurs at 12.74 V. This discrepancy exceeds the experimental error in the determination and indicates a failure of the Born approximation.