Molecular Vibration Spectra from Field-Emission Energy Distributions

Abstract

A calculation is presented which predicts the effect of an inelastic interaction between field-emitted electrons and adsorbed molecules at a metal–vacuum interface. The derivative of the total energy distribution of the field-emission current should yield information on the infrared absorption spectra of the adsorbed molecules. A numerical estimate of the size of the effect indicates that changes on the order of 1% of the total current should occur.

Field, Thermionic, and Secondary Electron Emission Spectroscopy

“…When the second derivative of the current (d 2 //dV2) is plotted against the applied voltage V one sees peaks at certain values of ·v corresponding to vibrational excitation energies of the metal-adsorbed-molecule complex. Flood (1970) was the first to point out that a similar situation could arise in a field emission experiment.…”

“…In a field emission experiment, an electron incident from within the metal with energy E may scatter inelastically off the vibrator (a metal-adatom or a metal-admolecule complex) leaving the metal with energy E -hwp. If the interaction between the tunneling electron and the vibrator is weak (so that it can be treated by first-order approximation theory) and if it is assumed that the vibrations associated with different atoms (molecules) do not interact with each other, the energy distribution of the field-emitted electrons is, to a first approximation, given by (Flood, 1970;Gadzuk and Plummer, 1973) jT…”

Necessary Conditions for Two-Lobe Patterns in Field Emission Microscopy

“…[2][3][4][5][6] Relatively complex total electron distributions were observed, which implies that electron transmission involves both elastic-and inelastic scattering processes. [7][8][9] In addition, high-resolution FEM has revealed complexities in cloverleaf patterns. It is still unclear whether cloverleaf patterns originate from the molecular shape or from electron wave interference.…”

“…Since small organic molecules have relatively complex structures with many bonds, it was quite difficult to determine the necessary conditions for cloverleaf patterns using small organic molecules. [1][2][3][4][5][6][7][8][9][10][11][12] Consequently, the present study employs many simple gas and liquid molecules in FEM measurements. The experimental results reveal some definite tendencies.…”