Comments on the use of implanted Ar as a binding energy reference

The binding energy of the Ar2p level of Ar implanted into insulating oxides has been determined via Au calibration. The Ar2p binding energy has been demonstrated to be constant at a binding energy of 242.3 ± 0.1 eV for a range of oxides including γ-Al₂O₃, ZrO₂, SiO₂ and Y₂O₃.     

Small-angle elastic scattering of 14.8 mev neutrons

The 14.8 MeV neutron elastic scattering differential cross sections of U, Pb, Hg, Ta, Sn and Al have been measured for angles extending from 10° down to 1.8° and for U and Pb down to 0.35°. Nuclear cross sections extrapolated to 0° have been compared with the Wick limit. The U nuclear cross sections did not rise as sharply toward 0°, and were not in as serious disagreement with the spherical optical model, as in earlier measurements. The smallest-angle data verified the Schwinger prediction.     

Leed and thermal desorption studies of small molecules (H2, O2, CO,CO2, NO,C2H4, C2H2 AND C) chemisorbed on the rhodium (111) and (100) surfaces

The chemisorption of H₂, O₂, CO, CO₂, NO, C₂H₄, C₂H₂ and C has been studied on the clean Rh(111) and (100) surfaces. LEED, AES and thermal desorption were used to determine the surface structures, disordering and desorption temperatures, displacement and decomposition characteristics for each species. All of the molecules studied readily chemisorbed on both surfaces. A large variety of ordered structures was observed, especially on the (111) surface. The disordering temperatures of most ordered surface structures on the (111) surface were below 100°C. It was necessary to adsorb the gases at 25° C or below in order to obtain well-ordered surface structures. Chemisorbed oxygen was readily removed from the surface by H₂ or CO gas at crystal temperatures above 50°C. CO₂ appears to dissociate to CO upon adsorption on both rhodium surfaces as indicated by the identical ordering and desorption characteristics of these two molecules. C₂H₄ and C₂H₂ also had very similar ordering and desorption characteristics and it is likely that the adsorbed species formed by both molecules is the same. Decomposition of ethylene produced a sequence of ordered carbon surface structures on the (111) face as a result of a bulk-surface carbon equilibrium. The chemisorption properties of rhodium appear to be generally similar to those of iridium, nickel and palladium.     

Methanol decomposition on platinum (111)

The interaction of methanol with clean and oxygen-covered Pt(111) surfaces has been examined with high resolution electron loss spectroscopy (EELS) and thermal desorption spectroscopy (TDS). On the clean Pt(111) surface, methanol dehydrogenated above 140 K to form adsorbed carbon monoxide and hydrogen. On a Pt(111)-p(2 × 2)O surface, methanol formed a methoxy species (CH₃O) and adsorbed water. The methoxy species was unstable above 170 K and decomposed to form adsorbed CO and hydrogen. Above room temperature, hydrogen and carbon monoxide desorbed near 360 and 470 K, respectively. The instability of methanol and methoxy groups on the Pt surface is in agreement with the dehydrogenation reaction observed on W, Ru, Pd and Ni surfaces at low pressures. This is in contrast with the higher stability of methoxy groups on silver and copper surfaces, where decomposition to formaldehyde and hydrogen occurs. The hypothesis is proposed that metals with low heats of adsorption of CO and H₂ (Ag, Cu) may selectively form formaldehyde via the methoxy intermediate, whereas other metals with high CO and H₂ chemisorption heats rapidly dehydrogenate methoxy species below room temperature.     

Nonlinear properties of vielbein massive gravity

We propose a nonlinear extension of the Fierz–Pauli mass for the graviton through a functional of the vielbein and an external Minkowski background. The functional generalizes the notion of the measure, since it reduces to a cosmological constant if the external background is formally sent to zero. Such a term and the explicit external background emerge dynamically from a bi-gravity theory, having both a massless and a massive graviton in its spectrum, in a specific limit in which the massless mode decouples, while the massive one couples universally to matter. We investigate the massive theory using the Stückelberg method and providing a ’t Hooft–Feynman gauge fixing, in which the tensor, vector and scalar Stückelberg fields decouple. We show that this model has the softest possible ultraviolet behavior that can be expected from any generic (Lorentz-invariant) theory of massive gravity, namely that it becomes strong only at the scale Λ₃=(m_g ²M_P)^1/3.     

Comparison of active and passive environmental sampling for safeguards applications

Towards development of electrical conductivity based sensors for online detection of formation of third phase during reprocessing of Pu rich spent nuclear fuels, laboratory studies were carried out using U⁴⁺ solutions in various experimental conditions. Third phases were generated by extracting U⁴⁺ from nitric acid medium by 1.09 M TBP at different A/O (A: aqueous, O: organic) ratios. The results of this study indicate that the third phase is nearly 100–300 times more conducting than lean organic phase and saturated phase. The higher conductivity of third phase as compared to that of other two phases is explained based on the principle of reverse micelle formation and charge movement between the micro emulsion globules by percolation phenomenon.