ESCA studies of molecular core and valence levels in the gas phase
The study of molecules in the gas phase by ESCA offers several advantages. Particularly, the opportunity to make direct comparisons between theoretical and experimental results is of importance. From such comparisons a more complete understanding of several fundamental phenomena in ESCA has been gained. The present paper reviews some recent work in Uppsala along this line. The effect of electron reorganization on core binding energies in atoms and molecules is analyzed. Chemical shifts in ESCA and n.m.r. are discussed. The existence of a general relation involving these chemical shifts and nuclear spin-rotation constants is pointed out. A model for analyzing ESCA intensities of the valence electrons in molecules is presented. It is shown that the analysis may be useful in identifying the molecular orbitals.
For most applications of ESCA it is highly desirable to improve the resolution and the intensity. An instrument, particularly designed to achieve this for gases, is discussed. It can also handle solid samples. It makes use of a high-emission, fine-focus electron gun, a rotating anode and a double focusing quartz crystal. The first electron spectrum recorded with this new instrument is presented.