[en] The behaviour of electrons in a metal is often compared to that of water in a pool. An empty pool is like a material that has all of its electrons removed. As electrons are 'poured' into the metal, they first occupy the lowest energies available - the bottom of the pool - and eventually fill up to the Fermi energy, the top of the pool. At this point we no longer discuss electrons but quasiparticles. These are electrons that have modified properties due to their interactions within the material. Waves in a pool can be excited, and their properties will depend on the depth of the water. Similarly in a metal, quasiparticles behave like waves that have a material-dependent dispersion relation between their energy and their wavevector, which specifies their direction and wavelength. This simple analogy also hints at an indirect method of measuring the dispersion relation of a metal, and hence the myriad of properties that depend on it. (U.K.)

[en] Photoabsorption spectra of gas-phase hydrogen sulfide and deuterium sulfide near the sulfur L_2,3 ionization thresholds have been measured using synchrotron radiation with high energy resolution from the SX700/II soft x-ray monochromator at BESSY. The spectra of both molecules are characterized by broad valence-shell absorption features 5-8 eV below the L₂ threshold energy and by many narrower Rydberg excitations 0-5 eV below the L₂ edge. Previously unobserved fine structure is resolved in both regions. Comparison of the H₂S and D₂S spectra allows the identification of transitions which include vibrational excitation, due to the isotopic dependence of vibrational energies. Least-squares analysis of the data indicates that the twofold degeneracy of the sulfur 2p_3/2 level is removed by the molecular field, with a resulting splitting of 115 meV for the higher-energy core-excited Rydberg states

[en] We have recently studied the threshold behavior of the K-shell photoelectron satellite/main line branching ratios in CO with high-resolution photoelectron spectroscopy and zero electron kinetic energy (ZEKE) spectroscopy. The electron time-of-flight measurements were performed at the Stanford Synchrotron Radiation Laboratory with a spherical grating monochromator. The ZEKE spectra above the Cls and Ols ionization thresholds show remarkable differences in the shake-up energy and intensity distribution of similar 1s-¹π- ¹π satellite states. The energy dependency of the branching ratios of eight Cls satellite states will be presented. In the region of the triplet coupled Cls-¹π-¹π satellite around 305 eV, we were able to resolve three components that show a variation in the branching ratios as a function of the photon energy

[en] This paper describes a new replacement system for the existing vibrations and loose parts monitoring system for the Arkansas Nuclear One (ANO) units 1 and 2, in Russellville, Arkansas. The installation and operational history are also discussed

[en] We have obtained analytic expressions for the sheath voltages and sheath widths for both collisional and collisionless sheaths driven by a combination of dc and rf voltage sources. A 'dc/rf sheath' develops on the negatively biased electrode while a typical rf sheath develops on the other electrode. The dc/rf sheath has a dc region with negligible electron density near the negatively biased electrode. Furthermore, if the rf power is held constant (typical for industrial plasmas driven by rf power sources), the sheath voltage drop of the rf sheath is nearly independent of the dc voltage provided the discharge configuration does not lead to a significant increase in the ionization efficiency of the secondary electrons. The analysis is done for both symmetric (equal area) and asymmetric diode discharges, as well as a triode configuration. The analytical results for the symmetric and asymmetric diode discharges are compared to the results of numerical simulations using plane-parallel and cylindrical particle-in-cell (PIC) codes over a wide range of pressures and rf frequencies, finding good agreement. The effect of secondary electrons is also examined with the PIC codes, finding increased discharge efficiency

[en] We present a comparison of patterned 193 nm photoresist (PR) line width roughness (LWR) of samples processed in a well characterized argon (Ar) inductively coupled plasma (ICP) system to RMS surface roughness and bulk chemical modification of blanket 193 nm PR samples used as control samples. In the ICP system, patterned and blanket PR samples are irradiated with Ar vacuum ultraviolet photons (VUV) and Ar ions while sample temperature, photon flux, ion flux and ion energy are controlled and measured. The resulting chemical modifications to bulk 193 nm PR (blanket) and surface roughness are analysed with Fourier transform infrared spectroscopy and atomic force microscopy (AFM). LWR of patterned samples are measured with scanning electron microscopy and blanket portions of the patterned PRs are measured with AFM. We demonstrate that with no RF-bias applied to the substrate the LWR of 193 nm PR tends to smooth and correlates with the smoothing of the RMS surface roughness. However, both LWR and RMS surface roughness increases with simultaneous high-energy (≥70 eV) ion bombardment and VUV-irradiation and is a function of exposure time. Both high- and low-frequency LWR correlate well with the RMS surface roughness of the patterned and blanket 193 nm PR samples. LWR, however, does not increase with temperatures ranging from 20 to 80 deg. C, in contrast to the RMS surface roughness which increases monotonically with temperature. It is unclear why LWR remains independent of temperature over this range. However, the fact that blanket roughness and LWR on patterned samples, both scale similarly with VUV fluence and ion energy suggests a similar mechanism is responsible for both types of surface morphology modifications.

[en] The authors report on the results of a search for superconductivity in Li. They find no evidence for the predicted transition to superconductivity at any temperature down to 5 mK in magnetic fields down to 0.5 microT. However, an unexpected Curie-Weiss Temperature dependence in the magnetic susceptibility is observed. They discuss the possibility that this signal arises from the Li itself, the possibility that it arises from Kondo behavior, and the implications of the effect for the predicted T_c of Li

[en] The study of photoelectron satellites in the near-threshold region is important for differentiating among various electron correlation mechanisms. For CO, which is a prominent test case for theories describing electron correlation effects, the threshold and near-threshold branching ratios (BR's) of the K-shell satellites were measured. Eight different C 1s satellite states were identified, showing very complex threshold behavior. The resonancelike behavior of the (2σ)^-1(1π)^-1(2π^*)¹(S'=1) satellite BR agrees with recent theoretical calculations. The observed energy dependence of the singlet (2σ)^-1(1π)^-1(2π^*)¹ satellite compares less well with the calculations. Three ²Σ⁺ satellites with a (2σ)^-1(5σ)^-1(nσ)¹ configuration have a constant satellite BR over the energy range studied. Three 2σ satellites, which have been assigned as pure conjugate shake-up states, have intensity only near threshold. The threshold spectrum above the O 1s ionization threshold consists of two distinct groups of satellites. Conjugate shake-up transitions contribute to the intense feature centered at 551-eV binding energy, which is not observed above its threshold. Two ²Σ⁺ satellites, which have been described by configuration interaction of (1σ)^-1(5σ)^-1(nσ)¹ states with a singlet ππ^* state, show indications of shape-resonance-like behavior

[en] High-resolution photoionization studies of He have revealed more than 50 states below the N=2--7 thresholds of He⁺, including sixteen (sp,2n+) and five (sp,2n-) states in the N=2 series. With a resolving power of E/ΔE congruent 10 000, states as narrow as 0.1 meV could be observed and linewidths were determined with an accuracy up to ±0.5 meV. Interchannel interferences, evident through effects on positions, shapes, and intensities of Rydberg lines, were interpreted within the framework of the multichannel quantum-defect theory

[en] The x-ray-absorption near-edge structure of gas-phase H₂S, hydrogen sulfide, and D₂S, deuterium sulfide, at the sulfur L_2,3 ionization thresholds has been measured using synchrotron radiation with high-energy resolution from the SX700/II soft-x-ray monochromator at the Berliner Elektronenspeicherring-Gessellschaft fuer Synchrotronstrahlung m.b.H. Previously unobserved fine structure is resolved. The spectra of both molecules are characterized by multielectron excitations 8--14 eV above the L₂ threshold energy, broad valence-shell absorption features 5--8 eV below the L₂ edge, and many narrower Rydberg excitations 0--5 eV below the L₂ edge. Comparison of the H₂S and D₂S spectra allows the identification of transitions which include vibrational excitation, due to the isotopic dependence of vibrational energies. For the (2p)^-1 core-excited Rydberg states, a least-squares analysis was employed, which deconvoluted the core-level and excited-orbital splittings. Results show that the twofold degeneracy of the sulfur 2p_3/2 core level is removed by the molecular field, with a resulting splitting of 115 meV for the higher-energy core-excited Rydberg states. The energies of the higher Rydberg states were well described by the Rydberg formula with the quantum defects δ_p=1.63 and δ_d=0.32. Fine structure was resolved in the transitions to the dissociative (2p)^-1 core-excited valence-shell states. The regular spacing and isotopic dependence of this structure clearly identifies it as a vibrational progression