J. A. Michejda

Electron transmission study of the temporary negative ion states of selected benzenoid and conjugated aromatic hydrocarbons

Electron transmission spectroscopy is utilized to determine the vertical electron affinities and to characterize the temporary anion states of a series of alternant hydrocarbons including benzene, naphthalene, anthracene, tetracene, styrene, and cis‐ and trans‐stilbene. The vibrational structure present in the low lying resonances is interpreted in light of the charge distributions of the temporarily occupied orbitals. The energies of the anion states are compared with the predictions of PPP, PPP‐CI, and HAM calculations, the pairing theorem and with the results from optical absorption measurements on the ground state anions in rigid glasses.

A study of the negative ion states of selected cyclodienes by electron transmission spectroscopy

Abstract Electron transmission spectroscopy is employed to locate sharp variations in the total cross sections for electrons scattered from several cyclic compounds containing two carboncarbon bonds. For each molecule, structure is observed which we associate with the temporary occupation of the two low-lying, normally unfilled, π * orbitals by impacting electrons. Electron affinities are reported for 1,5-cyclooctadiene, 1,4-and1,3-cyclohexadiene, norbornadiene and also cyclohexene, propene, and cis -butene.

Low-energy electron scattering from Mg, Zn, Cd and Hg: shape resonances and electron affinities

Measurements of electron scattering at low energy from Mg, Zn, Cd and Hg have been carried out using the electron transmission method. A large shape resonance is observed for each element which is identified with the (ns2np)2P ground state of the negative ion. The electron affinities in eV are found to be Mg(-0.15), Zn(-0.49), Cd(-0.33) and Hg(-0.63) with an error of +or-0.04 eV. The results are compared with the available theoretical predictions.

Electron transmission study of the formaldehyde electron affinity

Abstract We have employed electron transmission spectroscopy to detect sharp variations in the total scattering cross section of electron from formaldehyde resulting from temporary negative ion formation. A progression of peaks is observed which we identify with vibrational levels of the H 2 CO − ( 2 B 1 ) ground state. The adiabatic electron affinity of H 2 CO is found to be −0.65 ± 0.05 eV.

Detection of vibrationally excited nitrogen by trapped electron and electron transmission methods

Two techniques for detection of vibrationally excited nitrogen using low‐energy electron scattering are described. The first technique uses the trapped electron method to observe excitation from Nv2 into the B3Πg state near threshold. From the known Franck‐Condon factors, the contribution from excited vibrational levels may be unfolded. The second technique employs the electron transmission method to detect sharp structure in the total scattering cross section resulting from the formation of temporary negative ions. Because of uncertainties in the total scattering cross sections from each of the vibrational levels, the transmission method is less accurate than the trapped electron technique. As a consistency check, the vibrational temperature of N2 downstream from a microwave discharge is determined as a function of the discharge power. Within their respective error limits, the two methods are in good agreement.

Observation of vibrationally excited nitrogen with a simplified electron transmission apparatus

A simple electron transmission apparatus is used to observe vibrationally excited N2 in the first two vibrational levels. The method is based on the pronounced peaks appearing in the total electron scattering cross section in the range of energy 2–4 eV. Because of the wide spacing between these peaks, good energy resolution is not required and measurements can be performed without an electron monochromator.