Matrix isolation study of the photolysis of cyanogen azide. The infrared and ultraviolet spectra of the free radical NCN

Infrared and ultraviolet absorption spectra of free radical in photolysis of cyanogen azid

Matrix isolation study of the reaction of f atoms with co infrared and ultraviolet spectrum of the free radical fco

Matrix isolation of reaction of fluorine atoms with carbon monoxide - infrared and ultraviolet spectrum of free radical fluorocarbon monoxid

Time-dependent Internal DFT formalism and Kohn-Sham scheme

We generalize to the time-dependent case the stationary Internal DFT / Kohn-Sham formalism presented in Ref. [14]. We prove that, in the time-dependent case, the internal properties of a self-bound system (as an atomic nuclei) are all defined by the internal one-body density and the initial state. We set-up a time-dependent Internal Kohn-Sham scheme as a practical way to compute the internal density. The main difference with the traditional DFT / Kohn-Sham formalism is the inclusion of the center-of-mass correlations in the functional.Comment: 13 pages. To be published in Phys. Rev.

Gonadal hormones, but not sex, affect the acquisition and maintenance of a Go/No-Go odor discrimination task in mice

In mice, olfaction is crucial for identifying social odors (pheromones) that signal the presence of suitable mates. We used a custom-built olfactometer and a thirst-motivated olfactory discrimination Go/No-Go (GNG) task to ask whether discrimination of volatile odors is sexually dimorphic and modulated in mice by adult sex hormones. Males and females gonadectomized prior to training failed to learn even the initial phase of the task, which involved nose poking at a port in one location obtaining water at an adjacent port. Gonadally intact males and females readily learned to seek water when male urine (S+) was present but not when female urine (S−) was present; they also learned the task when non-social odorants (amyl acetate, S+; peppermint, S−) were used. When mice were gonadectomized after training the ability of both sexes to discriminate urinary as well as non-social odors was reduced; however, after receiving testosterone propionate (castrated males) or estradiol benzoate (ovariectomized females), task performance was restored to pre-gonadectomy levels. There were no overall sex differences in performance across gonadal conditions in tests with either set of odors; however, ovariectomized females performed more poorly than castrated males in tests with non-social odors. Our results show that circulating sex hormones enable mice of both sexes to learn a GNG task and that gonadectomy reduces, while hormone replacement restores, their ability to discriminate between odors irrespective of the saliency of the odors used. Thus, gonadal hormones were essential for both learning and maintenance of task performance across sex and odor type.We thank David Giese for help in programming the apparatus used in GNG testing and Alberto Cruz-Martin for comments on an early version of the manuscript. This work was supported by NIDCD grant DC008962 to JAC. (DC008962 - NIDCD grant)Accepted manuscrip

Strangeness Enhancement in Heavy Ion Collisions - Evidence for Quark-Gluon-Matter ?

The centrality dependence of (multi-)strange hadron abundances is studied for Pb(158 AGeV)Pb reactions and compared to p(158 GeV)Pb collisions. The microscopic transport model UrQMD is used for this analysis. The predicted Lambda/pi-, Xi-/pi- and Omega-/pi- ratios are enhanced due to rescattering in central Pb-Pb collisions as compared to peripheral Pb-Pb or p-Pb collisions. A reduction of the constituent quark masses to the current quark masses m_s \sim 230 MeV, m_q \sim 10 MeV, as motivated by chiral symmetry restoration, enhances the hyperon yields to the experimentally observed high values. Similar results are obtained by an ad hoc overall increase of the color electric field strength (effective string tension of kappa=3 GeV/fm). The enhancement depends strongly on the kinematical cuts. The maximum enhancement is predicted around midrapidity. For Lambda's, strangeness suppression is predicted at projectile/target rapidity. For Omega's, the predicted enhancement can be as large as one order of magnitude. Comparisons of Pb-Pb data to proton induced asymmetric (p-A) collisions are hampered due to the predicted strong asymmetry in the various rapidity distributions of the different (strange) particle species. In p-Pb collisions, strangeness is locally (in rapidity) not conserved. The present comparison to the data of the WA97 and NA49 collaborations clearly supports the suggestion that conventional (free) hadronic scenarios are unable to describe the observed high (anti-)hyperon yields in central collisions. The doubling of the strangeness to nonstrange suppression factor, gamma_s \approx 0.65, might be interpreted as a signal of a phase of nearly massless particles.Comment: published version, discussion on strange mesons and new table added, extended discussion on strange baryon yields. Latex, 20 pages, including 5 eps-figure

An absorption spectrum amplifier for determining gas composition

Compositions of gas samples are frequently studied by laser absorption spectroscopy. Sensitivity is improved by two orders of magnitude when absorption cell is placed inside an organic-dye laser cavity

Local Thermal and Chemical Equilibration and the Equation of State in Relativistic Heavy Ion Collisions

Thermodynamical variables and their time evolution are studied for central relativistic heavy ion collisions from 10.7 to 160 AGeV in the microscopic Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). The UrQMD model exhibits drastic deviations from equilibrium during the early high density phase of the collision. Local thermal and chemical equilibration of the hadronic matter seems to be established only at later stages of the quasi- isentropic expansion in the central reaction cell with volume 125 fm$^{3}$. distributions at all collision energies for $t\geq 10 fm/c$ with a unique Baryon energy spectra in this cell are approximately reproduced by Boltzmann rapidly dropping temperature. At these times the equation of state has a simple form: $P \cong (0.12-0.15) \epsilon$. At 160 AGeV the strong deviation from chemical equilibrium is found for mesons, especially for pions, even at the late stage of the reaction. The final enhancement of pions is supported by experimental data.Comment: 17 Pages, LaTex, 8 eps figures. Talk given at SQM'98 conference, 20-24 July 1998, Padova, Italy, submitted to J. Phys.

Slow imbalance relaxation and thermoelectric transport in graphene

We compute the electronic component of the thermal conductivity (TC) and the thermoelectric power (TEP) of monolayer graphene, within the hydrodynamic regime, taking into account the slow rate of carrier population imbalance relaxation. Interband electron-hole generation and recombination processes are inefficient due to the non-decaying nature of the relativistic energy spectrum. As a result, a population imbalance of the conduction and valence bands is generically induced upon the application of a thermal gradient. We show that the thermoelectric response of a graphene monolayer depends upon the ratio of the sample length to an intrinsic length scale l_Q, set by the imbalance relaxation rate. At the same time, we incorporate the crucial influence of the metallic contacts required for the thermopower measurement (under open circuit boundary conditions), since carrier exchange with the contacts also relaxes the imbalance. These effects are especially pronounced for clean graphene, where the thermoelectric transport is limited exclusively by intercarrier collisions. For specimens shorter than l_Q, the population imbalance extends throughout the sample; the TC and TEP asymptote toward their zero imbalance relaxation limits. In the opposite limit of a graphene slab longer than l_Q, at non-zero doping the TC and TEP approach intrinsic values characteristic of the infinite imbalance relaxation limit. Samples of intermediate (long) length in the doped (undoped) case are predicted to exhibit an inhomogeneous temperature profile, whilst the TC and TEP grow linearly with the system size. In all cases except for the shortest devices, we develop a picture of bulk electron and hole number currents that flow between thermally conductive leads, where steady-state recombination and generation processes relax the accumulating imbalance.Comment: 14 pages, 4 figure