The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites

No abstract available

Simulation of the photodetachment spectrum of HHfO- using coupled-cluster calculations

The photodetachment spectrum of HHfO? was simulated using restricted-spin coupled-cluster single-double plus perturbative triple {RCCSD(T)} calculations performed on the ground electronic states of HHfO and HHfO?, employing basis sets of up to quintuple-zeta quality. The computed RCCSD(T) electron affinity of 1.67 ± 0.02 eV at the complete basis set limit, including Hf 5s25p6 core correlation and zero-point energy corrections, agrees well with the experimental value of 1.70 ± 0.05 eV from a recent photodetachment study [X. Li et al., J. Chem. Phys. 136, 154306 (2012)]. For the simulation, Franck-Condon factors were computed which included allowances for anharmonicity and Duschinsky rotation. Comparisons between simulated and experimental spectra confirm the assignments of the molecular carrier and electronic states involved but suggest that the experimental vibrational structure has suffered from poor signal-to-noise ratio. An alternative assignment of the vibrational structure to that suggested in the experimental work is presented

Causality bounds for neutron-proton scattering

We consider the constraints of causality and unitarity for the low-energy interactions of protons and neutrons. We derive a general theorem that non-vanishing partial-wave mixing cannot be reproduced with zero-range interactions without violating causality or unitarity. We define and calculate interaction length scales which we call the causal range and the Cauchy-Schwarz range for all spin channels up to J = 3. For some channels we find that these length scales are as large as 5 fm. We investigate the origin of these large lengths and discuss their significance for the choice of momentum cutoff scales in effective field theory and universality in many-body Fermi systems.Comment: 36 pages, 10 figures, 7 tables, version to appear in Eur. Phys. J.

On the vanishing viscosity limit in a disk

We say that the solution u to the Navier-Stokes equations converges to a solution v to the Euler equations in the vanishing viscosity limit if u converges to v in the energy norm uniformly over a finite time interval. Working specifically in the unit disk, we show that a necessary and sufficient condition for the vanishing viscosity limit to hold is the vanishing with the viscosity of the time-space average of the energy of u in a boundary layer of width proportional to the viscosity due to modes (eigenfunctions of the Stokes operator) whose frequencies in the radial or the tangential direction lie between L and M. Here, L must be of order less than 1/(viscosity) and M must be of order greater than 1/(viscosity)

Monte Carlo Simulation of Sinusoidally Modulated Superlattice Growth

The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating the substrate in the presence of an inhomogeneous flux distribution instead of successively closing and opening of source shutters is studied via Monte Carlo simulations. It is found that the concentration of each compound is sinusoidally modulated along the growth direction, caused by the uneven arrival of Se and Te atoms at a given point of the sample, and by the variation of the Te/Se ratio at that point due to the rotation of the substrate. In this way we obtain a ZnSe$_{1-x}$Te$_x$ alloy in which the composition $x$ varies sinusoidally along the growth direction. The period of the modulation is directly controlled by the rate of the substrate rotation. The amplitude of the compositional modulation is monotonous for small angular velocities of the substrate rotation, but is itself modulated for large angular velocities. The average amplitude of the modulation pattern decreases as the angular velocity of substrate rotation increases and the measurement position approaches the center of rotation. The simulation results are in good agreement with previously published experimental measurements on superlattices fabricated in this manner

Anisotropic Flow from RHIC to the LHC

Anisotropic flow is recognized as one of the main observables providing information on the early stage of a heavy-ion collision. At RHIC the large observed anisotropic flow and its successful description by ideal hydrodynamics is considered evidence for an early onset of thermalization and almost ideal fluid properties of the produced strongly coupled Quark Gluon Plasma. This write-up discusses some key RHIC anisotropic flow measurements and for anisotropic flow at the LHC some predictions.Comment: 4 pages, 6 figures, hotquarks 200

Ab initio calculations on SF2 and its low-lying cationic states: Anharmonic Franck-Condon simulation of the uv photoelectron spectrum of SF2

Geometry optimization calculations were carried out on the X (1)A(1) state of SF2 and the X B-2(1), A (2)A(1), B B-2(2), C B-2(2), D (2)A(1), and E (2)A(2) states of SF2+ employing the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] method and basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron (S 2s(2)2p(6) and F 1s(2) electrons) correlation and basis set extension to the complete basis set limit on the computed minimum-energy geometries and relative electronic energies (adiabatic and vertical ionization energies) were investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the X (1)A(1) state of SF2 and the low-lying states of SF2+ listed above employing the aug-cc-pV(5+d)Z and aug-cc-pV5Z basis sets for S and F, respectively. Anharmonic vibrational wave functions of these neutral and cationic states of SF2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T) PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron bands of SF2. The agreement between the simulated and observed first bands in the He I photoelectron spectrum reported by de Leeuw [Chem. Phys. 34, 287 (1978)] is excellent. Our calculations largely support assignments made by de Leeuw on the higher ionization energy bands of SF2

Contact pressure distribution in guide bearings for pneumatic actuators

This paper deals with the analysis of the contact pressure distribution at the rod/guide bearing interface of a linear pneumatic actuator. The investigation was carried out both experimentally, using pressure-sensitive film, and numerically by means of finite element analysis. By using the numerical model, it was possible to identify design changes to the cylinder front head whereby contact pressure at the bearing/rod interface can be redistributed. Operating conditions that are more advantageous in terms of wear and durability can thus be achieved

Lattice calculations for A=3,4,6,12 nuclei using chiral effective field theory

We present lattice calculations for the ground state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our results were previously summarized in a letter publication. This paper provides full details of the calculations. We include isospin-breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.Comment: 38 pages, 11 figures, final publication versio

Thomson and Compton scattering with an intense laser pulse

Our paper concerns the scattering of intense laser radiation on free electrons and it is focused on the relation between nonlinear Compton and nonlinear Thomson scattering. The analysis is performed for a laser field modeled by an ideal pulse with a finite duration, a fixed direction of propagation and indefinitely extended in the plane perpendicular to it. We derive the classical limit of the quantum spectral and angular distribution of the emitted radiation, for an arbitrary polarization of the laser pulse. We also rederive our result directly, in the framework of classical electrodynamics, obtaining, at the same time, the distribution for the emitted radiation with a well defined polarization. The results reduce to those established by Krafft et al. [Phys. Rev. E 72, 056502 (2005)] in the particular case of linear polarization of the pulse, orthogonal to the initial electron momentum. Conditions in which the differences between classical and quantum results are visible are discussed and illustrated by graphs