Characterization of Surfaces on an Aomic Scale by Field Ionization Energy Spectra

Field ionization energy spectra of toluene, cycloheptatriene and phenolare reported. Details of the spectra are correlated with molecular proper-ties. The implications of the observation for analytical work are discussed. INTRODUCTIONField Ionization has proven to be a useful tool in the mass spectrometricstudy of organic molecules. This paper presents data which suggest techniquesfor extending the information obtainable from field ionization mass spectrom-etry. High resolution energy analysis of field ionization products providesenergy spectra which correlate with nolecular properties. Such data canpotentially provide information useful in interpreting mass spectra as wellas in studying the field ionization of molecules.Energy analysis of organic molecular ions created at a field emitterhas established a linear relationship between appearance potentials measuredby various techniques and energy distribution onsets. ~ Specifically, forthe parent ion, with ionization potential I, a first order theory of distrl-bution onsets gives the onset energy deficit, AE (i.e. the ion energy asobserved referenced to the potential applied to the emitter), as AE I ^