K.D. Jordan

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.

Theoretical study of the binding of an electron to a molecular dipole: LiCl−

Ab initio calculations are carried out to determine the nature of the binding of the LiCl anion. The extra electron.is found to be in a predominantly nonbonding orbital on the lithium end of the molecule and the calculations predict an electron affinityu of LiCl of 0.54 eV. This is in good agreement with the experimental value of 0.61 eV, which has been recently determined by Carlsten, Peterson, and Lineberger. The ab initio results are discussed in light of the finite dipole model.

On the electron affinities of ethylene and 1,3-butadiene

Abstract Temporary negative ion formation in ethylene and 1,3-butadiene has been studied using high resolution, low energy electron scattering. Sharp structure in the total electron scattering cross section allows the adiabatic electron affinity of each molecule to be determined leading to values of −1.55 ± 0.1 eV for ethylene and −0.62 ± 0.05 eV for 1,3-butadiene.

Calculation of the Si–H bond energies for the monohydride phase of Si(100)

Ab initio calculations are carried out on Si9H12, Si9H13, and Si9H14 clusters, chosen to model the Si(100)–(2×1) reconstructed surface and its hydrides. A value of 56 kcal/mol is obtained for the energy of the recombinative hydrogen desorption. The energies required to remove the first and second H atoms from a doubly‐occupied site are 81 and 76 kcal/mol, respectively.

Temporary anions of the fluoroethylenes

Abstract Electron transmission spectroscopy is employed to measure the gas phase electron affinities of the fluoroethylenes. Fluorination is found to destabilize the π* anions with respect to that of ethylene. The role of bond length changes as well as inductive and resonance effects is examined.

On the existence of negative ions of nonionic polar molecules: Studies of HF−, H2O−, HCN−, (HF)−2, H3NO− and CH3CN−*

Abstract Ab initio calculations are presented which demonstrate that nonionic polar molecules with sufficiently large dipole moments can form stable anions by the attachment of electrons in their dipole fields. The resulting electron affinities are found to be considerably smaller than for ionic molecules with comparable dipole moments. As a result of our calculations we conclude that the dipole fields of HF and H 2 O are too weak to bind an electron. On the other hand, calculations on (HF) − 2 , H 3 NO and CH 3 CN − have been carried out which suggest that these species are stable. HCN − appears to be a borderline case; the present study indicates that it may be stable.

Theoretical study of stable negative ions of polar molecules: NaH−, LiH−, LiF−, BeO−

In order to investigate the nature of the binding of electrons to polar molecules, we have performed ab initio calculations on LiH, LiF, NaH, BeO, and their anions. The anions are predicted to be stable and our calculated vertical electron affinities of the parent molecules are 0.30, 0.46, 0.36, and 1.77 eV for LiH, LiF, NaH, and BeO, respectively. It is demonstrated that electron correlation effects are small in the binding of electrons to these polar molecules since the extra electron occupies a predominantly nonbonding orbital on the electropositive atom.

Use of Pade approximants in the construction of diabatic potential energy curves for ionic molecules

For most ionic molecules, sufficient experimental information is not available for the construction of an RKR potential curve; thus, model potentials have been employed which use some of the experimental information in their construction (e.g., Born‐Mayer and Rittner potentials). In this paper, we present a simple method for constructing model potential curves which allows one to use all the available experimental information and to easily incorporate new information as it becomes available. This method, employing a Pade approximant technique, is capable of predicting the value of higher Dunham coefficients to within experimental accuracy from a knowledge of the lower ones. Consequently, it also predicts some spectroscopic properties from a knowledge of other data to much better accuracy than the Rittner or Born‐Mayer models.

Electronic structure of small metal clusters. I. Anions of Be2, Be3, and Be4

Ab initio calculations have been carried out for Be, Be2, Be3, Be4, and their anions. Whereas Be− is unstable with respect to electron detachment, Be2, Be3, and Be4, posses stable negative ions. The electron affinity increases with cluster size as would be expected from simple perturbation theory considerations.

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.