AbstractSelected portions of theS0andT1potential energy surfaces of acetaldehyde surveyed in our earlier studies have been reexamined. The assumption of the additivity of basis‐set polarization and of electron correl...
AbstractSelected portions of theS0andT1potential energy surfaces of acetaldehyde surveyed in our earlier studies have been reexamined. The assumption of the additivity of basis‐set polarization and of electron correlation effects used extensively in our earlier work on acetaldehyde has been tested through explicit polarized basis‐set electron‐correlation calculations. The “additivity assumption” introduces average absolute errors in energy differences of only 1.9 (MP3) to 3.4 (MP2) kcal mol−1in seven comparisons. The effects of using 6‒31G**SCFoptimized geometries as opposed to single‐point calculations on 3‒21G SCF structures (6–31G**//3–21G) as in our previous papers were examined. In six comparisons, the average absolute error in relative SCF energies introduced by the use of the 3–21G geometries rather than the fully consistent 6–31G–ones was only 0.3 kcal mole−1. After a uniform scaling procedure, comparisons of the 6–31G**and 3–21G calculated vibrational frequencies with experiment for CH3CHO (S0), CH4, and CO (20 comparisons) yielded absolute differences of 41 cm−1(6–31G**) and 57 cm−1(3–21G). All these more elaborate calculations support for the specific case of acetaldehyde and various minima and transition states of relevance to its photochemistry, the commonly used and practically important approximations (e.g.
Some ideas as to what the important factors are that will produce a reliable indium O‐ring seal are discussed. Four novel indium seal designs which are based on these ideas are presented. Three of these seals have be...
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Some ideas as to what the important factors are that will produce a reliable indium O‐ring seal are discussed. Four novel indium seal designs which are based on these ideas are presented. Three of these seals have been incorporated in a Brillouin cell. They include a simple sapphire window seal, a filling line union, and a flange seal. All of them have withstood low temperatures down to 77 K and moderate pressures up to 177 bar. The fourth seal described is a Pyrex tube seal for a Raman cell.
The problem of chemisorbing a hydrogen atom on a Cu-Ni or Au-Pt disordered binary alloy (DBA) is addressed. The DBA is modeled by a semi-infinite linear array of atomic sites each of which is randomly occupied by an a...
The problem of chemisorbing a hydrogen atom on a Cu-Ni or Au-Pt disordered binary alloy (DBA) is addressed. The DBA is modeled by a semi-infinite linear array of atomic sites each of which is randomly occupied by an atom of either component. The electronic properties of such a DBA are obtained via a Green’s-function technique based on the coherent-potential (CP) approximation. The chemisorption process is described by the Anderson-Newns approach, which takes account of the intra-atomic electron interaction on the adatom. The chemisorption energy and the adatom charge transfer are then computed as a function of the alloy concentration. The calculations at the surface involve the solution of two coupled self-consistent equations, one being concerned with the CP on the surface atom and the other with the adatom occupancy. In the case of the Cu-Ni system, the effect of surface segregation is also investigated.
High‐density polyethylene has good spectral transmission characteristics in the range from 20–500 cm? 1. This, coupled with its ease of fabrication and low cost, make it an excellent choice for far‐infrared absorpt...
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High‐density polyethylene has good spectral transmission characteristics in the range from 20–500 cm?1. This, coupled with its ease of fabrication and low cost, make it an excellent choice for far‐infrared absorption cell windows which operate at room temperature. However, because of its relatively large thermal coefficient of expansion and its brittleness (at low temperatures), the usual type of polyethylene absorption cell windows are difficult to make leaktight at low temperatures, especially if there is a moderately high pressure inside the absorption cell. In this article the problems associated with the use of such windows at low temperatures and moderately high pressures are discussed and a successful window design which overcomes these problems is described. These windows have been incorporated in a cell which has been used to measure the collision‐induced absorption of various nonpolar gases at low temperatures. In these experiments the cell was cycled hundreds of times at pressures up to 96.5 bar and at temperatures down to 126 K.
Series of submerged arc welds of HSLA steel made with three different fluxes and metallic additions of Ti, Mo, and Cr have been examined to study the inclusions and their role in the nucleation of acicular ferrite. In...
I discuss current issues in hadron spectroscopy and their connection to Quantum Chromodynamics and to more general issues of hadron physics. The discussion is in elementary terms and is directed to non‐experts.
I discuss current issues in hadron spectroscopy and their connection to Quantum Chromodynamics and to more general issues of hadron physics. The discussion is in elementary terms and is directed to non‐experts.
Accurate measurements of the x-ray intensity ratio I(Kβ)/I(Kα) from electron-capture radionuclides, using Si(Li) detectors of calibrated line shape, eliminate an existing large discrepancy between experiment and rel...
Accurate measurements of the x-ray intensity ratio I(Kβ)/I(Kα) from electron-capture radionuclides, using Si(Li) detectors of calibrated line shape, eliminate an existing large discrepancy between experiment and relativistic Hartree-Fock predictions. Small systematic discrepancies in the literature ratios for the mechanisms of photoionization, and electron and proton excitation, are attributed to omission of radiative Auger (RA) satellites in spectrum analysis. With the inclusion of RA peaks in the spectrum fitting, the present data support Scofield’s predictions of I(Kβ)/I(Kα) at the 1% accuracy level, an important conclusion for elemental analysis techniques such as proton-induced x-ray emission and x-ray fluorescence. The resulting radiative Auger intensities also agree quite well with calculations.
Spectra in the wavelength range of 300–600 nm have been acquired during proton‐beam irradiation of samples of solid hydrogen and deuterium at 4.2 K. Emission spectra from the transitions A′?3Δ u →X? 3Σ? g of O...
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Spectra in the wavelength range of 300–600 nm have been acquired during proton‐beam irradiation of samples of solid hydrogen and deuterium at 4.2 K. Emission spectra from the transitions A′?3Δ u →X? 3Σ? g of O2, 4S–2 D of N?i, and 1 D–1 S of O?i have been measured and attributed to an air impurity in the sample. Comparison is made of the vibrational constants derived from the molecular bands, the spectral shifts of all features, and the lifetime of the 2p 32 D multiplet of N?i obtained in the solid hydrogens with those obtained by matrix isolation studies using N2 and rare gas hosts.
作者：
M. SteslickaM. RadnyS. G. DavisonQuantum Theory Group
Department of Applied Mathematics and Department of Physics University of Waterloo Waterloo Ontario Canada N2L?1 and Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Guelph Ontario Canada N1G?1
The effective-range approximation is adopted to study surface states of a linear array of scattering centers. It is shown that, depending on the values of the scattering length and effective range for the surface atom...
The effective-range approximation is adopted to study surface states of a linear array of scattering centers. It is shown that, depending on the values of the scattering length and effective range for the surface atom, two, one, or zero surface states can exist in the forbidden energy gap. The possibility of a smooth transition from true (stationary) surface states to virtual (decaying) states is discussed. A comparison is also made with the crystal-potential approach.
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