2,607 research outputs found

    Photoelectron spectra of anionic sodium clusters from time-dependent density-functional theory in real-time

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    We calculate the excitation energies of small neutral sodium clusters in the framework of time-dependent density-functional theory. In the presented calculations, we extract these energies from the power spectra of the dipole and quadrupole signals that result from a real-time and real-space propagation. For comparison with measured photoelectron spectra, we use the ionic configurations of the corresponding single-charged anions. Our calculations clearly improve on earlier results for photoelectron spectra obtained from static Kohn-Sham eigenvalues

    Bioethics and Armed Conflict: Moral Dilemmas of Medicine and War

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    Evaluation of the Free Energy of Two-Dimensional Yang-Mills Theory

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    The free energy in the weak-coupling phase of two-dimensional Yang-Mills theory on a sphere for SO(N) and Sp(N) is evaluated in the 1/N expansion using the techniques of Gross and Matytsin. Many features of Yang-Mills theory are universal among different gauge groups in the large N limit, but significant differences arise in subleading order in 1/N.Comment: 10 pages; no figures; LaTe

    Analytical solution of the Gross-Neveu model at finite density

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    Recent numerical calculations have shown that the ground state of the Gross-Neveu model at finite density is a crystal. Guided by these results, we can now present the analytical solution to this problem in terms of elliptic functions. The scalar potential is the superpotential of the non-relativistic Lame Hamiltonian. This model can also serve as analytically solvable toy model for a relativistic superconductor in the Larkin-Ovchinnikov-Fulde-Ferrell phase.Comment: 5 pages, no figures, revtex; vs2: appendix with analytical proof of self-consistency adde

    Reactions of polycyclic aromatic hydrocarbon radical cations with model biological nucleophiles

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    The determination of gas-phase reactivity of a series of polycyclic aromatic hydrocarbons (PAHs) with nucleophiles is directed at achieving isomer differentiation through ion-molecule reactions and collisionally activated decomposition spectra. A series of PAH isomers form gas-phase [adduci — H]+ ions with the reagent nucleophiles pyridine and N-methylimidazole. Collisionally activated decomposition spectra of the [adduct — H]+ ions of the pyridine/PAH systems are dominated by products formed by losses of C5H4N, C5H5N (presumably neutral pyridine), and C5H6N. Collisional activation of PAH/N-methylimidazole [adduct — H]+ ions causes analogous losses of C4H5N2, C4H6N2 (presumably neutral N-methylimidazole), and C4H7N2. The relative abundances of the ions that result from these losses are highly isomer specific for N-methylimidazole but less so for pyridine. Furthermore, PAH/N-methylimidazole [adduct — H]+ ions undergo a series of metastableion decompositions that also provide highly isomer-specific information. The C4H7N2 (from PAH/N-methylimidazole product ions) and C5H6N (from PAH/pyridine product ions) losses tend to increase with the ΔHf of the PAH radical cation. In addition, it is shown that the fragmentation patterns of these gas-phase PAH/nucleophile adducts are similar to fragmentation patterns of PAH/nucleoside adducts generated in solution, which suggests that the structures of products formed in gas-phase reactions are similar to those produced in solution
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