Harry J. T. Preston

MS Xα calculations on the chlorofluoromethanes

Abstract MS Xα calculations have been performed on the chlorofluoromethanes (CF4, CF3Cl, CF2Cl2, CFCl3, CCl4) to assess the applicability of this method for such mixed halomethanes. The agreement of the ionization potentials calculated from transition state energies with the experimentally measured photoelectron spectral ionization potentials was extremely good. The transition state procedure was also used to estimate the electron affinities of the chlorofluoromethanes. The results indicated that the electron affinities for CF4 and CF3Cl would be negative, those for CFCl3 and CCl4 should be possitive and that for CF2Cl2, while the calculations show it to be positive, the positive value was within the demonstrated inherent computational error of the calculational procedure.

MS-Xα calculations on boron trihalides and comparison with their photoelectron spectra☆

Abstract The multiple-scattering Xα model has been applied to the sequence of boron trihalides BX 3 where X = F.C1. Br, and I. Transition state calculations show good agreement with the experimental ionization potentials measured by photoelectron spectra.

Ab-initio configuration interaction calculations of hydronium ion excited states☆

Abstract Large-scale ab-initio configuration (CI) calculations have been performed to determine vertical excitation energies of C 3V H 3 O + for each of the two lowest singlet and triplet excited states of the A 1 , A 2 , and E symmetries. These calculations take into account all configuration functions (CFs) generated by single- and double-excitations of electrons from multiple reference CFs to a truncated space of “improved” virtual orbitals. Reference CFs for each state were determined from small CI calculations including up to several hundred CFs and the final CFs used to compute variational energies were selected from lists including up to 21 000 CFs by cumulative energy selection. The lowest vertical excited state of H 3 O + is predicted to be the 3 A 1 state followed by the 1 A 1 , the 3 E, and the 1 E states in order.