Photoionization cross sections in the valence electron approximation. III. Nonlinear molecules (theory)

A theoretical method involving the plane‐wave approximation and the use of semiempirical LCAO‐SCF‐MOs of the CNDO and MINDO type is developed for the calculation of photoionization cross sections of arbitrary molecules consisting of atoms from the first three rows of the Periodic Table. Three qualitative concepts for the interpretation of the formalism are discussed, and the dependence of the cross sections on the photon energy, on the electron density distribution in the initial orbital, and on the different behaviour of s, p, and d electrons is treated explicitly. Examples for the application to HeI and HeII photoelectron spectroscopy are given, too

The C₄H₄CO Potential Surface. Reactions Involving Bicyclo[2.1.0]pentenone

MNDO and MINDO/3 calculations were used to study the photochemical formation, thermal rearrangements, and dissociation of bicyclo[2.1.0]pentenone. The “forbidden” thermal conversion to cyclopentadienone requires little activation, which accounts for the low kinetic stability of bicyclo[2.1.0]pentenone. The theoretical results seem to be compatible with the available experimental evidence for the tri-tert-butyl-substituted systems and suggest an explanation for observed differences in reactivity

PHOTOIONIZATION CROSS SECTIONS: He I AND He II PHOTOELECTRON SPECTRA OF SATURATED THREE-MEMBERED RINGS

The relative band intensities in the He I and He II photoelectron spectra of cyclopropane, oxirane, and thirane are interpreted by means of a recent theoretical approach. For each compound, the assignment of the two bands in the 15–18 eV range derived from our intensity arguments is opposite to the sequence of the respective ab initio eigenvalues

PHOTOIONIZATION CROSS SECTIONS IN THE VALENCE ELECTRON APPROXIMATION. RELATIVE INTENSITIES IN THE HeI PHOTOELECTRON SPECTRA OF LINEAR MOLECULES

Theoretical and experimental values for the relative band intensities in the Hel-photoelectron spectra of eighteen linear molecules are compared. Qualitative rules concerning band intensities are discussed

PHOTOIONIZATION CROSS SECTIONS IN THE VALENCE ELECTRON APPROXIMATION. I. LINEAR MOLECULES

Expressions for the photoionization cross sections of valence molecular orbitals are given for linear molecules consisting of atoms from the first three rows of the Periodic Table. Preliminary results for HF, F2, HCl and Cl2 are compared with experimental values

MNDOC Study of Excited States

MNDOC calculations of excited states are carried out by using a CI perturbation treatment of electron correlation. MNDOC results for vertical and adiabatic excitation energies, geometries, and dipole moments are reported and compared with experimental and ab initio data. On the basis of this evidence, the application of MNDOC to the study of photochemical reactions is discussed