[en] This study concerns experimental results of a chemical-physical and mineralogical characterisation of some mortars, sampled by different masonries brought to light during excavations of the site of Monte Sannace. The aim of the research is to provide, through the characterisation of the mortar samples and the relative raw materials, useful information in order to define the stages of construction and the workers' technological knowledge during different historical periods. DTA/TG/DTG thermoanalytical investigations and X-ray diffractometry analyses can allow to define the nature of both the binder and aggregate materials. As regards a specific mortar with hydraulic behaviour such a study has allowed to recognise also the residual reactivity towards lime of the 'pozzolanic' sand, rich in volcanic ashes, used as aggregate in the original mortar. The thermoanalytical and X-ray diffractometric results together with the granulometric and chemical determinations allow to get information about the preparation techniques of binding materials of old masonries

[en] The laboratory energy distribution of H⁺ from the dissociation of H₃⁺ in low-keV H₃⁺-He collisions is measured at a 0 degree laboratory angle. An inelastic energy loss of Q=26±2 eV has been determined for the excited states of H₃⁺ that produce low-energy protons upon dissociation. An approximate projectile-frame energy distribution of H⁺ is also presented. Our results suggest that the near-zero projectile-frame energy protons are produced by either an electronic singlet excitation of the ground state of H₃⁺ to a distribution of 2¹E', 1¹E'', and 2 ¹A₂^'', or as an alternative mechanism, a triplet excitation of H₃⁺ to 1³E' accompanied by a simultaneous triplet excitation of the He target. In either case, the near-zero energy protons are produced by a three-body dissociation of the excited (H₃⁺)^*. In the case of the triplet excitation, there are no long-range correlations for the motion of the neutral H atoms. For the singlet excitation, the neutral H atoms' motion is correlated and the angle between them is near 180 degree. The effects of the long-range nature of the total potential between the fragments is discussed in terms of the hyperspherical coordinates

[en] The dominant processes for producing near-zero-energy projectile-frame protons in H₂⁺-He collisions at 4-keV ion energy have been experimentally identified. The 1sσ_u to 2pπ_u and 3dσ_g transitions that produce these protons occur at internuclear separations of the H₂⁺ ion that are 2.5--3 times the equilibrium separation

[en] The laboratory energy distribution of protons in coincidence with L_α photons produced in collision-induced dissociation of 4.0-keV H₂⁺ on He targets has been measured for protons that are collected along the incident-beam direction. An approximate energy distribution of proton--L_α-photon pairs in the projectile frame is obtained by transforming the measured laboratory distribution. The transformed results reveal that the dominant processes for production of near-zero energy projectile frame protons are the 1sσ_g to 2pπ_u and 3dσ_g transition at 2.5--3 times the equilibrium separation of H₂⁺. This transformation technique provides a simple method of identifying inelastic processes from the convoluted laboratory energy distributions of the fragments produced in the dissociative excitation of the H₂⁺ molecule

[en] DTA/TG analysis and XRD investigations were carried out on pastes of pozzolanic cement and a mixture of pozzolanic cement and fly ash from municipal solid waste in order to examine their relative hydration processes. The presence of fly ash, from a municipal solid waste incinerator, provoked in the first curing period the slowing of hydration reactions of calcium silicates of cement and formation of gypsum and ettringite. With the progress of hydration in the pastes the calcium silicate hydrate phase developed and formation of calcium chloroaluminate was observed. The compressive strength of the hardened pastes confirmed good solidification attained by the materials. The leaching test allowed the degree of stabilization of the fly ash in the hardened pastes to be determined. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

[en] The results of an investigation on the production of Group IIA atomic and molecular negative ion beams formed in a cesium-sputter negative ion source are presented. The sputtering material was formed by pressing pellets of stoichiometric mixtures of the Group IIA element carbonates and 10% copper powder. Negative ions of several alkaline-earth elements and their oxides have been observed. Beam intensities as high as 180 pA have been observed for Sr^-and 20 nA for SrO^-. (orig.)

[en] The laboratory energy distribution of protons in coincidence with an H^- ion, resulting from the dissociation of excited H₃⁺, has been measured for H⁺-H^- pairs emitted along the beam for 4.0-keV H₃⁺-He collisions. An approximate energy distribution of H⁺-H^- pairs for the collinear configuration of the dissociation products is obtained by transforming the measured laboratory spectrum to the H₃⁺ center-of-mass (c.m.) frame. Coincidence data suggest that the reaction producing H⁺-H^- pairs where the H⁺ ion has near-zero energies (<0.5 eV) in the c.m. frame is a low-probability process. We have also computed the adiabatic Born-Oppenheimer energies of H₃⁺ ions using a full configuration-interaction calculation with a basis set of atomic orbitals consisting of 1s, 1s', 1p', 2s, and 2p centered on the protons forming an isosceles (C_2v symmetry) or an equilateral (D_3h symmetry) triangle. The states leading to asymptotic H⁺+H⁺+H^- limits have been identified by calculating left-angle 1/r₁₂ right-angle ^-1, the inverse of the expectation value of the electron-electron repulsion term. The states identified by this procedure have adiabatic Born-Oppenheimer energies of 40--45 eV above the H₃⁺ ground state at the H₃⁺ equilibrium separation. The limits on the total available internal energy to be shared by the three dissociation products that one obtains from the experimentally determined H⁺-H^- coincidence spectrum are consistent with the identified H₃⁺ excited states

[en] The electron affinity of lanthanum has been measured using laser photoelectron energy spectroscopy. This is the first electron affinity measurement for lanthanum and one of the first measurements of an electron affinity of a rare-earth series element. The electron affinity of lanthanum was measured to be 0.47±0.02 eV. At least one bound excited state of La^- was also observed in the photoelectron spectra, and the binding energy relative to the ground state of lanthanum was measured as 0.17±0.02 eV. The present experimental measurements are compared to a recent calculation. (author). Letter-to-the-editor

[en] We measured the laboratory energy distribution of H⁺-H^- pairs in coincidence, at 0 with respect to the beam direction, produced by 4.0 keV H⁺₂ colliding with Xe and He. The transformation of the laboratory energy distribution of H⁺-H^- pairs in coincidence from the laboratory frame to the center-of-mass frame shows that, contrary to the earlier measurements, the charge transfer to the dissociative excited H₂ state releases a substantial amount of maximum kinetic energy (∼ 4 eV/ion) which suggests that H⁺-H^- pairs result from the dissociation of doubly excited states of H₂. These doubly excited states of H^**₂ are formed by an electron transfer-excitation process which is studied in molecules for the first time. The energies of these doubly excited states have been calculated by Guberman and are consistent with our measurements of the H⁺-H^- energies. The dissociation process proceeds from covalent doubly excited states through states of mixed doubly and singly excited configurations, to states of mixed ionic and covalent configurations, to a final pure ionic state. The details of this transformation are still open to conjecture and await further theory and calculations. (orig.)

[en] The spectral dependence of the angular distributions of photoelectrons produced by the single-photon detachment of Al^-, Si^-, and P^- ions has been measured at five discrete photon wavelengths ranging from 457.9 to 647.1 nm (2.71 endash 1.92 eV) using a crossed laser-ion beam apparatus. Values of the asymmetry parameter have been determined by fits to the photoelectron yield as a function of the angle between the laser polarization vector and the linear momentum vector of the collected photoelectrons. The experimental results for Al^- are compared with a recent theoretical calculation [C. N. Liu and A. F. Starace, Bull. Am. Phys. Soc. 42, 1026 (1997)] and are found to be in good agreement. copyright 1997 The American Physical Society