Molecular‐orbital experiments

Abstract

Molecular orbitals (MO) are theoretical entities created to describe probability functions of bonding electrons in molecular groups. Whereas one‐electron wave functions that describe atomic orbitals have been measured for decades by spectrographic techniques, bonding electrons in molecules have been less discrete objects to measure directly. The ultimate hopes of those engaged in applied MO theory in the field of mineral physics ride on being able to deduce the nature of bonding electrons precisely.A new application of the so‐called Penning ionization principle may make these hopes realizable; it offers the first opportunity to obtain by direct measurement quantitative electron densities within the outer orbitals. Called a Penning ionization electron spectroscopy (PIES) technique, this potentially major breakthrough in molecular orbital studies was developed by Koichi Ohno, Hideki Mutoh, and Yoshiya Harada of the University of Tokyo. As described recently, the results of the University of Tokyo group have shown that “ … a spectroscopic technique can provide information about individual molecular orbitals and that … [the technique] … is most sensitive to the outer most orbitals” (Chemical and Engineering News, August 1, 1983).