Lo I. Yin

Apollo 15 Geochemical X-ray Fluorescence Experiment: Preliminary Report

Although only part of the information from the x-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.

X-Ray Photoelectron Spectroscopic Studies of Valence States Produced by Ion-Sputtering Reduction:

X-ray photoelectron spectroscopic measurements of various valence states of Fe and Cu in several compounds using ion-sputtering reduction are presented, and the potential usefulness of this time-dependent and in situ method is discussed.

Core Binding Energy Difference between Bridging and Nonbridging Oxygen Atoms in a Silicate Chain

The x-ray photoelectron spectra of the oxygen 1s level of olivines contain a single component whereas those of pyroxenes contain two components with an intensity ratio of 2:1 and an energy separation of about 1 electron volt. We interpret these two components to be the result of the binding energy differences between nonbridging and bridging oxygen atoms within a silicate chain in the pyroxene structure.

Apollo 15 and 16 results of the integrated geochemical experiment

A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface. The observations involved measurements of secondary (fluorescent) X-rays, gamma rays and alpha particle emissions. A large scale compositional map of over 20% of the lunar surface was obtained for the first time. It was possible to demonstrate significant chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the Moons hidden side.

Trace element partitioning between ionic crystal and liquid

The partitioning of trace elements between ionic crystals and the melt has been correlated with lattice energy of the host. The solid-liquid partition coefficient has been expressed in terms of the difference in relative ionic radius of the trace element and the homogeneous and heterogeneous strain of the host lattice. Predictions based on this model appear to be in general agreement with data for alkali nitrates and for rare-earth elements in natural garnet phenocrysts.

Some parameters affecting Auger and photoelectron spectroscopy as an analytical technique.

Various possibilities of Auger and photoelectron spectroscopy as an analytical technique are discussed. In some applications simple electrostatic analyzers with coarse resolution may suffice and even be preferable. Typical spectra obtained with a hemispherical electrostatic analyzer of 0.6% energy resolution are presented and discussed. Such factors as sample thickness, sample potential, surface contamination, and incident angle of the exciting x rays have been found to affect the quality and character of the observed spectra. These results characterize some of the features, problems, and capabilities of applied Auger and photoelectron spectroscopy.

Interatomic Auger transitions in maximal valent V and Cr compounds

The Auger and x‐ray photoelectron spectra of V and Cr compounds, where V and Cr exist in their maximal valence state with nominal 3d 0 electron configuration, have been studied. In these compounds, the mere presence of Auger peaks involving the 3d electrons unequivocally identifies their interatomic character. Furthermore, using ion bombardment to induce valence state reductions of transition metal ions, we are able to observe dynamically, and in situ, the interatomic to intra‐atomic transitions of the Auger spectra. In particular, the intensity of the cation L3M23M45 transitions has been observed to increase dramatically with ion bombardment. The correlation between the interatomic Auger transition and covalency as well as the movements of the 3d electrons are also discussed.