Tung Tsang

Paramagnetism and shake-up satellites in X-ray photoelectron spectra

Abstract The correlation between paramagnetism and the shake-up satellites in the X-ray photoelectron spectra of the 3d transitional-metal compounds is examined and explained in terms of modified selection rules governing the shake-up transitions.

XPS studies of ion-bombardment damage of transition metal sulfides

Abstract Radiation damage to the surface of transition metal sulfides under ∼1-keV ion bombardment has been investigated by photoelectron spectroscopy. Under

XPS studies of ion bombardment damage of iron—sulfur compounds

Abstract Chemical reduction on the surface of iron—sulfur compounds due to ion bombardment has been studied by photoelectron spectroscopy (XPS or ESCA). In addition to the “chemical” nature of surface reduction due to excitations and interactions of valence electrons, radiation-induced changes may also involve such factors as ion—surface chemical interactions and the volatilities of the components. Specifically, the data suggest that after ion bombardment, the reduced metallic iron co-exists with the relatively non-volatile elemental sulfur on the surface, in contrast to the loss of the volatile anion components from halogen and oxygen compounds.

Interpretation of Auger satellites in Co, Ni, and Cu compounds

Abstract X-ray photoelectron spectra of the 2p levels of Co, Ni, and Cu compounds are examined concurrently with their L3M4,5M4,5 Auger spectra. A correlation is established between the presence or absence of Auger satellites with the presence or absence of photoelectron shake-up satellites for Co and Ni compounds. The correlation is less clear for cupric compounds. We propose the mechanism of Auger shake-up as a plausible interpretation for the observed behavior of these Auger satellites.

Dynamics of interacting Brownian particles

Abstract A memory function formulation has been used for the dynamics of interacting Brownian particles in colloidal systems and polymer dispersions. By introducing approximations at the level of the force correlation function, the theoretical scattering functions agree well with the experimental photon correlation spectroscopy data.

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.