The mean free path for electron conduction in metallic fullerenes

We calculate the electrical resistivity due to electron-phonon scattering for a model of A3C60 (A= K, Rb), using an essentially exact quantum Monte-Carlo calculation. In agreement with experiment, we obtain exceptionally large metallic resistivities at large temperatures T. This illustrates that the apparent mean free path can be much shorter than the separation of the molecules. An interpretation of this result is given. The calculation also explains the linear behavior in T at small T.Comment: 4 pages, RevTeX, 3 eps figure, additional material available at http://www.mpi-stuttgart.mpg.de/docs/ANDERSEN/fullerene

In-Situ Infrared Transmission Study of Rb- and K-Doped Fullerenes

We have measured the four IR active $C_{60}$ molecular vibrations in $M_{x}C_{60}$ $(M = K, Rb)$ as a function of doping $x$. We observe discontinuous changes in the vibrational spectra showing four distinct phases (presumably $x = 0, 3, 4$, and 6). The $1427cm^{-1}$ and $576cm^{-1}$ modes show the largest changes shifting downward in frequency in four steps as the doping increases. Several new very weak modes are visible in the $x=6$ phase and are possibly Raman modes becoming weakly optically active. We present quantitative fits of the data and calculate the electron-phonon coupling of the $1427cm^{-1}$ IR mode.Comment: 3 pages, Figure 1 included, 3 more figures available by request. REVTEX v3.0 IRC60DO

NOGAPS-ALPHA model simulations of stratospheric ozone during the SOLVE2 campaign

This paper presents three-dimensional prognostic O₃ simulations with parameterized gas-phase photochemistry from the new NOGAPS-ALPHA middle atmosphere forecast model. We compare 5-day NOGAPS-ALPHA hindcasts of stratospheric O₃ with satellite and DC-8 aircraft measurements for two cases during the SOLVE II campaign: (1) the cold, isolated vortex during 11-16 January 2003; and (2) the rapidly developing stratospheric warming of 17-22 January 2003. In the first case we test three different photochemistry parameterizations. NOGAPS-ALPHA O₃ simulations using the NRL-CHEM2D parameterization give the best agreement with SAGE III and POAM III profile measurements. 5-day NOGAPS-ALPHA hindcasts of polar O₃ initialized with the NASA GEOS4 analyses produce better agreement with observations than do the operational ECMWF O₃ forecasts of case 1. For case 2, both NOGAPS-ALPHA and ECMWF 114-h forecasts of the split vortex structure in lower stratospheric O₃ on 21 January 2003 show comparable skill. Updated ECMWF O₃ forecasts of this event at hour 42 display marked improvement from the 114-h forecast; corresponding updated 42-hour NOGAPS-ALPHA prognostic O₃ fields initialized with the GEOS4 analyses do not improve significantly. When NOGAPS-ALPHA prognostic O₃ is initialized with the higher resolution ECMWF O₃ analyses, the NOGAPS-ALPHA 42-hour lower stratospheric O₃ fields closely match the operational 42-hour ECMWF O₃ forecast of the 21 January event. We find that stratospheric O₃ forecasts at high latitudes in winter can depend on both model initial conditions and the treatment of photochemistry over periods of 1-5 days. Overall, these results show that the new O₃ initialization, photochemistry parameterization, and spectral transport in the NOGAPS-ALPHA NWP model can provide reliable short-range stratospheric O₃ forecasts during Arctic winter

Anomalous Nuclear Quantum Effects in Ice

One striking anomaly of water ice has been largely neglected and never explained. Replacing hydrogen ($^1$H) by deuterium ($^2$H) causes ice to expand, whereas the "normal" isotope effect is volume contraction with increased mass. Furthermore, the anomaly increases with temperature $T$, even though a normal isotope shift should decrease with $T$ and vanish when $T$ is high enough to use classical nuclear motions. In this study, we show that these effects are very well described by {\it ab initio} density functional theory. Our theoretical modeling explains these anomalies, and allows us to predict and to experimentally confirm a counter effect, namely that replacement of $^{16}$O by $^{18}$O causes a normal lattice contraction.Comment: 5 pages, 3 figure

DCC Dynamics in (2+1)D-O(3) model

The dynamics of symmetry-breaking after a quench is numerically simulated on a lattice for the (2+1)-dimensional O(3) model. In addition to the standard sigma-model with temperature-dependent Phi^4-potential the energy functional includes a four-derivative current-current coupling to stabilize the size of the emerging extended topological textures. The total winding number can be conserved by constraint. As a model for the chiral phase transition during the cooling phase after a hadronic collision this allows to investigate the interference of 'baryon-antibaryon' production with the developing disoriented aligned domains. The growth of angular correlations, condensate, average orientation is studied in dependence of texture size, quench rate, symmetry breaking. The classical dissipative dynamics determines the rate of energy emitted from the relaxing source for each component of the 3-vector field which provides a possible signature for domains of Disoriented Chiral Condensate. We find that the 'pions' are emitted in two distinct pulses; for sufficiently small lattice size the second one carries the DCC signal, but it is strongly suppressed as compared to simultaneous 'sigma'-meson emission. We compare the resulting anomalies in the distributions of DCC pions with probabilities derived within the commonly used coherent state formalism.Comment: 27 pages, 17 figures; several minor insertions in the text; two references adde