Lo I Yin

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.

L‐S coupling interpretation of high‐resolution LMM Auger spectra of Cu and Zn

High‐resolution LMM Auger spectra of Cu and Zn obtained by x‐ray excitation are shown to contain fine structures which have not been reported previously. An attempt has been made to classify these fine structures in terms of pure L‐S coupling of the final vacancies of the atom. The agreement between the calculated and the observed energy separations of the fine‐structure lines is good within the accuracy of the Hartree‐Fock approximation.

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

A portable X-ray imaging system for small-format applications

A prototype low-intensity x-ray imaging system with the acronym LIXIscope was built to demonstrate the feasibility of a modular approach toward X-ray imaging in small-format applications. The prototype, including its own X-ray source, is shown to be fully portable, rugged and pocket-sized. Preliminary results and performance characteristics obtained with the prototype Lixiscope are presented.

X‐Ray Excited LMM Auger Spectra of Copper, Nickel, and Iron

Photoelectron and Auger‐electron spectra are both obtained with x‐ray excitation. Using the photoelectron spectra as internal energy standards, the energies of the prominent LMM Auger lines in Cu, Ni, and Fe have been accurately determined. In addition, the photoelectron spectra provide a measure of the vacancy distribution created by the x rays among the three L subshells. Thus, knowing both the energy values and the vacancy distribution, we have assigned the three prominent Auger lines of Cu, Ni, and Fe to be of type L3MM rather than L2MM.

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.

Quasi-atomic L-MM Auger spectra of solid Cu and Zn

Abstract Experimental L 3 -M 4,5 M 4,5 Auger spectra of metallic Cu and Zn show distinct characteristics of free-atom spectra but do not reflect the band structure. This quasi-atomic phenomenon in solids is tentatively explained as electron localization due to increased screening.

A small rugged imaging X-ray spectrometer: A lixiscope with good energy resolution

Abstract A new prototype Lixiscope (Low Intensity X-ray Imaging Scope) is described for operation in the 20–200 keV region. In addition to good spatial resolution, the new prototype is capable of providing simultaneous gamma-ray or X-ray single-photon counting, imaging, and energy resolution. The observed energy resolution determined from gamma-ray pulse-height spectra is only a factor of two poorer than that of a NAI(T1)-PMT (photomultipler tube) system. Taking into account the good spatial resolution, such a Lixiscope is thus equivalent to operating thousands of NaI(T1)-PMT systems in parallel with minimal degradation in overall energy resolution. These characteristics make the new prototype Lixiscope a compact and rugged device eminently suited for possible low-flux imaging applications.

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.

XPS studies of surface damages of transition metal fluorosilicates under argon ion bombardment

Radiation damages to the surfaces of transition metal fluorosilicates under l keV argon ion bombardment have been investigated by photoelectron spectroscopy. The damage sequences appear to be related to the inertness of the metal as well as the single valence states of Si and F. Near the middle of the transition series (FeSiF6), and for the d10 closed shell configuration (ZnSiF6), there is direct decomposition into the highly stable metal fluoride with the concomittant loss of the volatile SiF4. Thus, we observe the disappearance of Si 2p peak but not the F ls peak under prolonged ion bombardment. In contrast, near the end of the transition series, (Cu, Ni, Co)SiF6, where the metal is more inert, the cation and anion behave essentially as separate entities. Whereas the reduction of cation to metal occurs rather quickly (∼ 5 × 1017 ions/cm2), the decomposition of the anion into volatile components (SiF4 and F2) occur considerably later (∼ 60 × 1017 ions/cm2). Experimentally we observe the disappearance of both Si and F peaks. On the other hand, no radiation damage was observed on either alkali or alkaline earth fluorosilicates (Na2SiF6, K2SiF6, CaSiF6) where the 3d electrons are absent. Thus the resistance to radiation damage may be related to the absence of 3d electrons as well as to the single valence states of Si and F. These results underscore the chemical nature of surface damages under ion bombardment.