Kimio Ohno

Penning ionization electron spectroscopy of CO and Fe(CO)5. Study of electronic structure of Fe(CO)5 from electron distribution of individual molecular orbitals

The He* Penning ionization electron spectra (PIES) and He I UV photoelectron spectra (UPS) of CO and Fe(CO)5 were measured. The relative intensity of the bands in PIES was shown to give information on the spatial electron distribution of individual molecular orbitals. On the basis of the information together with the results of the population analysis, most of the bands in the UPS of Fe(CO)5 were assigned. The usefulness of PIES in the study of stereochemistry was indicated.

Modified Atomic Orbital Method. I. The Electronic Structure of the Ethylene Molecule

It is well known that the energy intervals separating ionic and covalent states, as given by the conventional ASMO method, are too large. In order to avoid this difficulty, a modification of the nonempirical atomic orbital method is proposed, and is applied to the ethylene molecule. The principal point of the modification is to use different atomic orbitals for covalent and ionic structures of the molecules in order to assess more correctly the energies of the ionic structures. The results of the calculation are fairly satisfactory in that they are as good as those of the semiempirical method by Moffitt. Some errors due to assumptions and approximations made in this calculation are discussed.

On the Valence Theory of the Methyl Radical

The electronic structure of the ground state of CH 3 is investigated by the Heitler-London-Slater-Pauling method extended by Voge and Kotani and Siga. The wave functions are constructed without assuming the electron pair bond and taking (2 s ) 2 (2 p ) 2 , (2 s )(2 p ) 3 and (2 p ) 4 configurations of the carbon atom into account. Assuming a pyramidal model for this radical, seventeen 2 A 1 states are obtained. The energy matrix for these states is computed by means of the representation matrices of the symmetric group. Solving the secular equation thus obtained for various values of the apex angle, the most stable configuration is found to be slightly nonplanar. The electron pair bond approximation is shown to be fairly good in the cases when \(\angle\)HCH=120° and 109.5° ( s p 1 and s p 3 hybridization), but it becomes very poor for \(\angle\)HCH=90° (pure p bond).

Quantum Mechanics of Electronic Structure of Simple Molecules

The subject of discussion in this article is the quantum-mechanical theory of simple molecules, i.e., systems consisting of N electrons and several nuclei, forming a stable entity. As is well known, such molecules can rotate and vibrate, and give rise to series of rotational and vibrational energy levels. Our main concern in the present article is, however, with the motion of electrons in these molecules, and rotations and vibrations of the molecules will not be dealt with in detail.

Modified Atomic Orbital Method. II. The Electronic Structure of the Oxygen Molecule

A modified form of the nonempirical atomic orbital method, shown previously to be considerably successful in calculating the electronic energy levels of the ethylene molecule, is now applied to the computation of the lower excited π‐electron levels of the oxygen molecule. The results of the calculation are again satisfactory in that they are almost as good as those obtained by the semiempirical methods of Moffitt and of Fumi and Parr.

Non-empirical Calculation of the Diamagnetic Anisotropy of Benzene

The large anisotropy of the diamagnetic susceptibility of benzene, which is considered to be due to the free migration of re-electrons, is calculated by the antisymmetrized LCAO-MO method. We have included all the configurations obtained by excitation of one or two electrons from the lowest configuration and we have retained all the many-center integrals. The calculated value of the diamagnetic anisotropy is about 50% of the experimental value. The effect of configuration interaction is not small enough to be neglected.

COLLISIONS BETWEEN NON-SPHERICAL MOLECULES. I. MOLECULAR COLLISIONS IN HYDROGEN GAS AT LOWER TEMPERATURES

Collisions between an atom and a diatomic molecule are theoretically investigated. The detailed calculations are carried out in the special case of hydrogen gas at lower temperatures in order to interpret the observed relation between the viscosity of the gas and the para-ortho concentration ratio. It is found that, by improving the· shape of the intermolecular potential, one can avoid the greater part of the discrepancy between the experimental fact and the result of an older theory. However, quantitative explanation of the relation requires more detailed and exhaustive calculations.

Theory of Intermolecular Potential and Second Virial Coefficient of Hydrogen at Low Temperature

The intermolecular potential between hydrogen molecules is calculated taking into account its dependence on the relative orientation of the molecules. Assuming that the rotational quantum number of each molecule is a good quantum number throughout collision at low temperature, the matrix elements of the repulsive short‐range intermolecular potential and the London potential are calculated. If the intermolecular potential depends on the relative orientation of colliding molecules, the resulting matrix element depends on the rotational quantum number. Thus it is pointed out that the second virial coefficient of ordinary hydrogen (which is, at low temperature, a mixture of 75 percent of J = 1 molecule and 25 percent of J = 0 molecules, where J is the rotational quantum number), and pure para hydrogen (which consists of only J = 0 molecules at low temperature) must be different, even if there were no statistical effect. The virial coefficient is calculated for very low temperature by solving the Schrodinger e...

Hfs of the H2S Molecule and Its Electronic Structure

The observed hfs coupling constant of the H2S33 molecule shows a large asymmetry although the H–S–H bond angle is known to be almost 90°. It is shown in this paper that a nonzero d character of the S–H bond orbital can explain this result. Assuming that the electron distribution is cylindrically symmetric about each S–H bond, and the radial part of the p‐ and d‐wave functions are the same, 10.5% s character, 73.5% p character, and 16% d character is concluded for the bond orbital; 23% p character and 77 percent s character is assigned for the lone pair. If the ionic structure is neglected, the electric quadrupole moment of the S33 nucleus is estimated to be —0.11×10—24 cm2.