Volumetric and infrared measurements on amorphous ice structure

We have simultaneously used adsorption isotherm volumetry and Fourier transform infrared spectroscopy in order to take the investigations on amorphous ice structure a step further, especially concerning porosity and annealing-induced modifications. We have studied surface reorganization during annealing and found that the number of surface sites decreases before crystallization, their relative ratios being different for amorphous and crystalline ice. We also present results confirming that ice can have a large specific surface area and nevertheless be non-microporous.     

DIC Challenge 2.0: Developing Images and Guidelines for Evaluating Accuracy and Resolution of 2D Analyses

Experimental Mechanics - The DIC Challenge 2.0 follows on from the work accomplished in the first Digital Image Correlation (DIC) Challenge Reu et al. (Experimental Mechanics 58(7):1067, 1). The...     

Core level photoemission study of Au deposited on Pt(111) in the submonolayer range

A photoemission study, using a synchrotron source, on the deposition of submonolayer amounts of Au on Pt(111) has been performed. The Au 4f emission shifts continuously to higher binding energies for increasing Au coverages. A good fit to the experimental spectra has been obtained by only one Doniac-Sunjic function. We discuss the initial versus final state effects in photoemission experiments on small supported particles.     

ESCA studies of some copper and silver selenides

Photoelectron and Auger spectra have been obtained for the copper and silver selenides CuSe, Cu ₂Se, Ag ₂Se, and AgCuSe as well as from CuS, Ag ₂O, Ag ₂S, Cu, and Ag. Binding-energy values, chemical shifts, and peak-shapes are reported for the Cu 3 d, Ag 4 d and Se 3 p electrons. Absence of multiplet splitting and shake-up structure is discussed in relation to the magnetic properties. It is shown that chemical shifts are much better revealed in the Auger spectra (Cu L₃M_4,5M_{4, 5} and Ag M₅N_{4, 5}N_{4, 5}) than in the direct photoelectron ones. In addition the use of the Auger parameter to characterize the series under study is emphasized. Finally the valence-band spectra have been examined and the electronic structures are interpreted.     

Ultrafast dynamics of acetylacetone (2,4-pentanedione) in the S2 state

The dynamics of the enolic form of acetylacetone (E-AcAc) was investigated using a femtosecond pump-probe experiment. The pump at 266 nm excited E-AcAc in the first bright state, S2(pi pi*). The resulting dynamics was probed by multiphoton ionization at 800 nm. It was investigated for 80 ps on the S2(pi pi*) and S1(n pi*) potential energy surfaces. An important step is the transfer from S2 to S1 that occurs with a time constant of 1.4 +/- 0.2 ps. Before, the system had left the excitation region in 70 +/- 10 fs. An intermediate step was identified when E-AcAc traveled on the S2 surface. Likely, it corresponds to an accidental resonance in the detection scheme that is met along this path. More importantly, some clues are given that an intramolecular vibrational energy relaxation is observed, which transfers excess vibrational energy from the enolic group O-H to the other modes of the molecule. The present multistep evolution of excited E-AcAc probably also describes, at least qualitatively, the dynamics of other electronically excited beta-diketones.     

Structure cristallographique et magnetique de Cr1−xTixN a basse temperature

Cr_1?xTi_xN solid solutions have at room temperature a crystallographic structure of NaCl type. The space group is Fm3m. The compounds with x ? 0.15 present at low temperature an antiferromagnetic order of the fourth kind and show an orthorhombic distorsion. The space group of the deformed phase is Pnmm. The magnetic moment measured by neutron diffraction decreases with increasing titanium concentration. The compounds with x ? 0.20 do not show any magnetic order and any crystallographic distortion at very low temperature.     

In‐plane and out‐of‐plane defects of graphite bombarded by H,D and He investigated by atomic force and Raman microscopies

Graphite samples exposed to H, D and He plasma at fluencies from 10¹⁶ to 10¹⁸ cm⁻² have been investigated by means of atomic force and Raman microscopies. The ion energy was varied between 40 and 800 eV, and the ion incidence was either perpendicular (Highly Oriented Pyrolitic Graphite) or parallel (carbon/carbon composite) to the basal plane. When increasing the impinging ion energy, the growth of nanometric domes at the surface has been observed by atomic force microscopy and the incident kinetic energy has been found as the parameter determining their height. Two different Raman signatures related to (1) a graphitic nano‐crystalline component similar to that of a 10¹⁴ cm⁻² bombarded 1‐, 2‐ and 3‐layer graphene, and to (2) an amorphous component, have been evidenced. Polarization studies have revealed that these components are related to regions with either in‐plane or out‐of‐plane disorder, coexisting in the material. These Raman studies have also revealed that both the defect–defect distance in the first case and the aromatic domain size in the second case are typically 1 nm. When the number of vacancies created in the material increases, the number of in‐plane defects decreases to the benefit of the out‐of‐plane defects. Copyright © 2014 John Wiley & Sons, Ltd.