Vincent McKoy

Bio: Vincent McKoy is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Photoionization & Scattering. The author has an hindex of 51, co-authored 369 publications receiving 10686 citations. Previous affiliations of Vincent McKoy include University of Paris & University of Notre Dame.

Studies of differential and total photoionization cross sections of molecular nitrogen

Abstract: The photoionization of molecular nitrogen has been studied using a frozen-core Hartree-Fock final-state wave function with a correlated intitial-state wave function. The final-state wave function was obtained using the iterative Schwinger variational method. The effects of initial-state correlation were studied by comparing cross sections obtained using a configuration-interaction-type initial-state wave function with those obtained using a Hartree-Fock initial-state wave function. In this paper we compare our accurate single-center expansion results with other theoretical results. We find that earlier single-center cross sections were not well converged with respect to their expansion parameters. The results of the continuum multiple-scattering method and the Stieltjes-Tchebycheff moment-theory approach are found to be in qualitative but not quantitative agreement with the present results. We also compare our computed total cross sections as well as integrated target angular distributions with experimental results for photoionization leading to the $X^{2}\ensuremath{\Sigma}_{g}^{+}$, $A^{2}\ensuremath{\Pi}_{u}$, and $B^{2}\ensuremath{\Sigma}_{u}^{+}$ states of ${\mathrm{N}}_{2}^{+}$. We find generally good agreement, which is improved by the inclusion of initial-state correlation effects, especially in the resonant photoionization channel leading to the $X^{2}\ensuremath{\Sigma}_{g}^{+}$ state of ${\mathrm{N}}_{2}^{+}$. We also report integrated detector angular distributions for these three channels.

Theory of Dissociation Pressures of Some Gas Hydrates

Abstract: Dissociation pressures of some gas hydrates have been evaluated using the Lennard‐Jones 12–6, 28–7, and Kihara potentials in the Lennard‐Jones‐Devonshire cell model. The Lennard‐Jones 28–7 potential gives the least satisfactory results. The Lennard‐Jones 12–6 potential works satisfactorily for the monatomic gases and CH4 but poorly for the rodlike molecules C2H6, CO2, N2, O2, C2H4. This failure may be due to (i) distortions of the hydrate lattice, (ii) neglect of molecular shape and size in determining the cavity potential (iii) barrier to internal rotation of the molecule in its cavity. A crude model for the lattice shows that it is not distorted. The Kihara potential predicts better dissociation pressures for the hydrates of the rodlike molecules. Unlike the previously used Lennard‐Jones 12–6 potential, it depends on the size and shape of the interacting molecules. The absence of lattice distortions, improved dissociation pressures through the use of the Kihara potential and the restriction of the motio...

Nonempirical Calculations on Excited States: The Ethylene Molecule

Abstract: A series of nonempirical calculations are reported on the excited states of the ethylene molecule using a recent minimum basis set LCAO MO SCF wavefunction. For the lowest excited singlet state of ethylene (^1B_(3u)) the coupling between the π electrons and σ electrons is significant: the excitation energy being decreased from 11.98 to 10.17 eV and the oscillator strength from 1.03 to 0.73. This coupling has little effect on the triplet state. In the next higher approximation (the random‐phase approximation) the excitation energy is further decreased to 9.44 eV and the transition moment to 0.51. With the use of accurate LCAO MO SCF wavefunctions, it is felt that the methods presented here will provide a basis for the theoretical interpretation of electronic spectra.

Extension of the Schwinger variational principle beyond the static-exchange approximation

Abstract: We propose a new vairational principle for scattering theory which extends the Schwinger variational principle beyond the static-exchange approximation and to inelastic scattering. Application of this formulation to the scattering of electrons by hydrogen atoms at energies below k^2=0.64 demonstrates the rapid convergence of the phase shift with respect to the number of basis functions for both the open- and closed-channel orbitals. Furthermore, we show that the convergence of the phase shift with respect to the number of expansion functions (exact states or pseudostates) is also fast. In our theory, the resulting phase shifts can be more accurate than those of the close-coupling method even if the same expansion basis is used. The phase shifts in our 1s-2s―-2p― calculation are comparable to those of 1s-2s-2p-3p―-3d― calculation of Matese and Oberoi [Phys. Rev. A 4, 569 (1971)], which are very close to the exact values. Several aspects of the convergence characteristics are also discussed.

Electron-Molecule and Photon-Molecule Collisions

Abstract: Application of the Close-Coupling Method to Electron-Molecule Scattering.- The Coupled-Channels Integral-Equations Method in the Theory of Low-Energy Electron-Molecule Scattering.- Roundtable on Numerical Methods.- Contribution of the Variable Phase Method to the Frame Transformation Theory of Rotational Excitation of Molecules by Electron Impact.- The R-Matrix Method for Electron-Molecule Scattering: Theory and Computation.- The T-Matrix Method in Electron-Molecule Scattering.- Roundtable on L2-Methods.- The Separable Approximation in Multichannel Electron-Molecule Collisions.- Nonempirical Polarization in Low-Energy Electron-Molecule Scattering Theory.- R-Matrix Calculations for Electron Scattering by Diatomic Molecules.- Discussion on Electron-Molecule Scattering.- Polarization Potentials for Electron Scattering.- Vibrational Excitations of Low-Energy e-CO Scattering.- Improved Hybrid Theory Calculation of e-N2 Vibrational Excitation.- Stieltjes-Tchebycheff Moment-Theory Approach to Molecular Photoionization Studies.- The Continuum Multiple-Scattering Approach to Electron-Molecule Scattering and Molecular Photo ionization.- Molecular Resonance Phenomena.- Stieltjes-Moment-Theory Technique for Calculating Resonance Widths.- Progress Toward the Application of Complex Coordinte and Complex Basis Function Techniques to Molecular Resonance Calculations.- Discussion on Photoionization and Molecular Resonances.- A Modification of the Langhoff Imaging Technique.- Workshop on L2-Methods.- Workshop on Single-Center Techniques.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Toward reliable density functional methods without adjustable parameters: The PBE0 model

Abstract: We present an analysis of the performances of a parameter free density functional model (PBE0) obtained combining the so called PBE generalized gradient functional with a predefined amount of exact exchange. The results obtained for structural, thermodynamic, kinetic and spectroscopic (magnetic, infrared and electronic) properties are satisfactory and not far from those delivered by the most reliable functionals including heavy parameterization. The way in which the functional is derived and the lack of empirical parameters fitted to specific properties make the PBE0 model a widely applicable method for both quantum chemistry and condensed matter physics.

Double-slit photoelectron interference in strong-field ionization of the neon dimer.

Abstract: Wave-particle duality is an inherent peculiarity of the quantum world. The double-slit experiment has been frequently used for understanding different aspects of this fundamental concept. The occurrence of interference rests on the lack of which-way information and on the absence of decoherence mechanisms, which could scramble the wave fronts. Here, we report on the observation of two-center interference in the molecular-frame photoelectron momentum distribution upon ionization of the neon dimer by a strong laser field. Postselection of ions, which are measured in coincidence with electrons, allows choosing the symmetry of the residual ion, leading to observation of both, gerade and ungerade, types of interference.

Design of Density Functionals by Combining the Method of Constraint Satisfaction with Parametrization for Thermochemistry, Thermochemical Kinetics, and Noncovalent Interactions.

Abstract: We present a new hybrid meta exchange-correlation functional, called M05-2X, for thermochemistry, thermochemical kinetics, and noncovalent interactions. We also provide a full discussion of the new M05 functional, previously presented in a short communication. The M05 functional was parametrized including both metals and nonmetals, whereas M05-2X is a high-nonlocality functional with double the amount of nonlocal exchange (2X) that is parametrized only for nonmetals. In particular, M05 was parametrized against 35 data values, and M05-2X is parametrized against 34 data values. Both functionals, along with 28 other functionals, have been comparatively assessed against 234 data values: the MGAE109/3 main-group atomization energy database, the IP13/3 ionization potential database, the EA13/3 electron affinity database, the HTBH38/4 database of barrier height for hydrogen-transfer reactions, five noncovalent databases, two databases involving metal−metal and metal−ligand bond energies, a dipole moment databas...