Low temperature electron transfer in strongly condensed phase

Electron transfer coupled to a collective vibronic degree of freedom is studied in strongly condensed phase and at lower temperatures where quantum fluctuations are essential. Based on an exact representation of the reduced density matrix of the electronic+reaction coordinate compound in terms of path integrals, recent findings on the overdamped limit in quantum dissipative systems are employed. This allows to give for the first time a consistent generalization of the well-known Zusman equations to the quantum domain. Detailed conditions for the range of validity are specified. Using the Wigner transform these results are also extended to the quantum dynamics in full phase space. As an important application electronic transfer rates are derived that comprise adiabatic and nonadiabatic processes in the low temperature regime including nuclear tunneling. Accurate agreement with precise quantum Monte Carlo data is observed.Comment: 16 pages, 6 figures, revised version with minor change

Divergence alone cannot guarantee stable sparse activity patterns if connections are dense

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Electron Transfer in Donor-Acceptor Systems: Many-Particle Effects and Influence of Electronic Correlations

We investigate electron transfer processes in donor-acceptor systems with a coupling of the electronic degrees of freedom to a common bosonic bath. The model allows to study many-particle effects and the influence of the local Coulomb interaction U between electrons on donor and acceptor sites. Using the non-perturbative numerical renormalization group approach we find distinct differences between the electron transfer characteristics in the single- and two-particle subspaces. We calculate the critical electron-boson coupling alpha_c as a function of $U$ and show results for density-density correlation functions in the whole parameter space. The possibility of many-particle (bipolaronic) and Coulomb-assisted transfer is discussed.Comment: 4 pages, 4 figure

Detection of liquid xenon scintillation light with a Silicon Photomultiplier

We have studied the feasibility of a silicon photomultiplier (SiPM) to detect liquid xenon (LXe) scintillation light. The SiPM was operated inside a small volume of pure LXe, at -95 degree Celsius, irradiated with an internal Am-241 alpha source. The gain of the SiPM at this temperature was estimated to be 1.8 x 10^6 with bias voltage at 52 V. Based on the geometry of the setup, the quantum efficiency of the SiPM was estimated to be 22% at the Xe wavelength of 178 nm. The low excess noise factor, high single photoelectron detection efficiency, and low bias voltage of SiPMs make them attractive alternative UV photon detection devices to photomultiplier tubes (PMTs) for liquid xenon detectors, especially for experiments requiring a very low energy detection threshold, such as neutralino dark matter searches

The Rational Overhauser: an Interpolating Rational Cubic Curve.

A rational interpolating cubic curve which implicitly maintains first order geometric continuity in splines has been developed. The curve is formed by blending two rational quadratic curves. Since the blending method used was originally introduced by Overhauser, this curve is referred to as the Rational Overhauser (Rover) curve. The curve formulation utilizes four shape factors to provide control of the curve. A geometrical and analytical interpretation of these shape factors and their relationship to each other is discussed. Procedures for representing conic sections using the rational Overhauser curve are presented. Also included are techniques for mapping between the Rover curve and rational forms of the Hermite, Bezier, and B-Spline curves

Self-assembled guanine ribbons as wide-bandgap semiconductors

We present a first principle study about the stability and the electronic properties of a new biomolecular solid-state material, obtained by the self-assembling of guanine (G) molecules. We consider hydrogen-bonded planar ribbons in isolated and stacked configurations. These aggregates present electronic properties similar to inorganic wide-bandgap semiconductors. The formation of Bloch-type orbitals is observed along the stacking direction, while it is negligible in the ribbon plane. Global band-like conduction may be affected by a dipole-field which spontaneously arises along the ribbon axis. Our results indicate that G-ribbon assemblies are promising materials for biomolecular nanodevices, consistently with recent experimental results.Comment: 7 pages, 3 figures, to be published in Physica

Playing "America" on Nineteenth-Century Stages; Or, Jonathan in England and Jonathan at Home

"Playing America," prepared towards the completion of a Ph.D. in Theatre and Performance Studies at the University of Pittsburgh, examines "Yankee Theatre" in America and London through a post-colonial lens from 1787 to 1855. Actors under consideration include: Charles Mathews, James Hackett, George Hill, Danforth Marble and Joshua Silsbee. These actors were selected due to their status as iconic performers in "Yankee Theatre."The Post-Revolutionary period in America was filled with questions of national identity. Much of American culture came directly from England. American citizens read English books, studied English texts in school, and watched English theatre. They were inundated with English culture and unsure of what their own civilization might look like. A post-colonial crisis, in other words, gripped the new nation. This dissertation attempts to explain "Yankee Theatre," a performance tradition popular from the mid-1820s to the mid-1850s, within this complex, transatlantic, sociopolitical situation. It begins with a discussion of early Yankee plays and explains how they were written against the "empire," distinguishing the new citizen from the English subject. It examines ways early Yankee Theatre actors expressed their American identity and discusses the pressures these actors faced in fighting for international success. "Yankee Theatre" was not only popular in America. Several American actors also traveled across the Atlantic to perform it on London stages. Thus, this dissertation also encompasses how the English understood the Yankee, how an imperial standard was established overseas, why English audiences were unhappy with the first American Yankee actors they witnessed, and how future Yankee actors were caught in this web of criterion and taste for years to come. "Playing America" asserts that "Yankee Theatre" addressed specific problems, issues, and questions arising from America's post-colonial status. When the post-colonial crisis passed, Yankee Theatre also ended. By the mid-to late-1850s, the minstrel replaced Jonathan as the symbol of the nation. An examination of "Yankee Theatre" allows for a greater understanding of circum-Atlantic performance as well as issues of nationalism and national identity in the theatre. Research methodologies include historical and textual analysis as well as post-colonial, literary, and dramatic theory

Van der Waals bond lengths and electronic spectral shifts of the benzene---Kr and benzene---Xe complexes

Rotationally resolved UV-spectra are presented for the 610 bands of benzene---Kr and benzene---Xe complexes yielding precise rotational constants and van der Waals bond lengths for the ground and excited vibronic state, and electronic band shifts. These value complement the previously published data for the other rare gases and the various quantities have now been determined for all the benzene—rare gas complexes. Measured values of the bond length were used to calculate the band shifts from recent theoretical predictions. They are compared with the experimental values of this work