A general maximum entropy principle for self-gravitating perfect fluid

We consider a self-gravitating system consisting of perfect fluid with spherical symmetry. Using the general expression of entropy density, we extremize the total entropy $S$ under the constraint that the total number of particles is fixed. We show that extrema of $S$ coincides precisely with the relativistic Tolman-Oppenheimer-Volkoff (TOV) equation of hydrostatic equilibrium. Furthermore, we apply the maximum entropy principle to a charged perfect fluid and derive the generalized TOV equation. Our work provides a strong evidence for the fundamental relationship between general relativity and ordinary thermodynamics.Comment: 13 pages, no figure. The arguments have been improved so that the assumption p=p(\rho) is no longer neede

Momentum Spectra of Electrons Rescattered from Rare-Gas Targets Following Their Extraction by One- and Two-Color Femtosecond Laser Pulses

We have used velocity-map imaging to measure the three-dimensional momenta of electrons rescattered from Xe and Ar following the liberation of the electrons from these atoms by 45 fs, 800 nm intense laser pulses. Strong structure in the rescattering region is observed in both angle and energy, and is interpreted in terms of quantitative rescattering (QRS) theory. Momentum images have also been taken with two-color (800 nm + 400 nm) pulses on Xe targets. A strong dependence of the spectra on the relative phase of the two colors is observed in the rescattering region. Interpretation of the phase dependence using both QRS theory and a full solution to the time-dependent Schrödinger equation shows that the rescattered electrons provide a much more robust method for determining the relative phase of the two colors than do the direct electrons

Orientation Dependence of the Ionization of CO and NO in an Intense Femtosecond Two-Color Laser Field

Two-color (800- and 400-nm) short (45-fs) linearly polarized pulses are used to ionize and dissociate CO and NO. The emission of Cq+, Nq+, and O⁺ fragments indicates that the higher ionization rate occurs when the peak electric field points from C to O in CO and from N to O in NO. This preferred direction is in agreement with that predicted by Stark-corrected strong-field-approximation calculations

Electrochemical characterization and surface analysis of bulk amorphous alloys in aqueous solutions at different pH

Bulk amorphous alloys are a new class of materials with a variety of characteristics that make them useful for applications in aqueous environments. While some bulk amorphous metals show increased corrosion resistance, there is still a lack of fundamental electrochemical studies of these materials. Two different compositions of BeCuNiTiZr bulk amorphous alloys have been studied at pH 5, 7, and 10 using cyclic voltammetry (CV), x-ray photoelectron spectroscopy (XPS), depth profiling methods, and optical microscopy. While XPS is used to determine the composition of the resulting oxide films, the CV curves and optical micrographs are compared to pinpoint differences in the corrosion resistance of the amorphous multicomponent alloys. The effect of the amorphicity, multicomponent structure and the presence of elements with widely varying interfacial reactivities on the oxidation process and on the corrosion resistance of the alloys, are discussed with the desire to provide some electrochemical background for the expected wide spread use of bulk amorphous alloys

Thermodynamics of a black hole in a cavity

We present a unified thermodynamical description of the configurations consisting on self-gravitating radiation with or without a black hole. We compute the thermal fluctuations and evaluate where will they induce a transition from metastable configurations towards stable ones. We show that the probability of finding such a transition is exponentially small. This indicates that, in a sequence of quasi equilibrium configurations, the system will remain in the metastable states till it approaches very closely the critical point beyond which no metastable configuration exists. Near that point, we relate the divergence of the local temperature fluctuations to the approach of the instability of the whole system, thereby generalizing the usual fluctuations analysis in the cases where long range forces are present. When angular momentum is added to the cavity, the above picture is slightly modified. Nevertheless, at high angular momentum, the black hole loses most of its mass before it reaches the critical point at which it evaporates completely.Comment: 27 pages, latex file, contains 3 figures available on request at [email protected]

On the investigations of galaxy redshift periodicity

In this article we present a historical review of study of the redshift periodicity of galaxies, starting from the first works performed in the seventies of the twentieth century until the present day. We discuss the observational data and methods used, showing in which cases the discretization of redshifts was observed. We conclude that galaxy redshift periodisation is an effect which can really exist. We also discussed the redshift discretization in two different structures: the Local Group of galaxies and the Hercules Supercluster. Contrary to the previous studies we consider all galaxies which can be regarded as a structure member disregarding the accuracy of velocity measurements. We applied the power spectrum analysis using the Hann function for weighting, together with the jackknife error estimator. In both the structures we found weak effects of redshift periodisation.Comment: 10 pages, 4 figures, to be published in Part. and Nucl. Lett. 200

Large-Angle Electron Diffraction Structure in Laser-Induced Rescattering from Rare Gases

We have measured full momentum images of electrons rescattered from Xe, Kr, and Ar following the liberation of the electrons from these atoms by short, intense laser pulses. At high momenta the spectra show angular structure (diffraction) which is very target dependent and in good agreement with calculated differential cross sections for the scattering of free electrons from the corresponding ionic cores

Field-free orientation of CO molecules by femtosecond two-color laser fields

We report the first experimental observation of non-adiabatic field-free orientation of a heteronuclear diatomic molecule (CO) induced by an intense two-color (800 and 400 nm) femtosecond laser field. We monitor orientation by measuring fragment ion angular distributions after Coulomb explosion with an 800 nm pulse. The orientation of the molecules is controlled by the relative phase of the two-color field. The results are compared to quantum mechanical rigid rotor calculations. The demonstrated method can be applied to study molecular frame dynamics under field-free conditions in conjunction with a variety of spectroscopy methods, such as high-harmonic generation, electron diffraction and molecular frame photoemission

Auger decay and subsequent fragmentation pathways of ethylene following K-shell ionization

Citation: Gaire, B., Haxton, D. J., Sturm, F. P., Williams, J., Gatton, A., Bocharova, I., . . . Weber, T. (2015). Auger decay and subsequent fragmentation pathways of ethylene following K-shell ionization. Physical Review A, 92(1), 13. doi:10.1103/PhysRevA.92.013408The fragmentation pathways and dynamics of ethylene molecules after core ionization are explored using coincident measurements of the Auger electron and fragment ions by employing the cold target recoil-ion momentum spectroscopy method. The influence of several factors on the dynamics and kinematics of the dissociation is studied. These include propensity rules, ionization mechanisms, symmetry of the orbitals from which the Auger electrons originate, multiple scattering, conical intersections, interference, and possible core-hole localization for the double ionization of this polyatomic molecule. Energy correlation maps allow probing the multidimensional potential energy surfaces and, in combination with our multiconfiguration self-consistent field calculations, identifying the populated electronic states of the dissociating dication. The measured angular distributions of the Auger electrons in the molecular frame further support and augment these assignments. The deprotonation and molecular hydrogen ion elimination channels show a nearly isotropic Auger electron angular distribution with a small elongation along the direction perpendicular to the molecular axis. For the symmetric breakup the angular distributions show a clear influence of multiple scattering on the outgoing electrons. The lowest kinetic energy release feature of the symmetric breakup channel displays a fingerprint of entangled Auger and photoelectron motion in the angular emission pattern identifying this transition as an excellent candidate to probe core-hole localization at a conical intersection of a polyatomic molecule.Additional Authors: Landers, A. L.;Belkacem, A.;Dorner, R.;Weber, T

Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields

Citation: Li, H., Mignolet, B., Wachter, G., Skruszewicz, S., Zherebtsov, S., Sussmann, F., . . . Kling, M. F. (2015). Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields. Physical Review Letters, 114(12), 6. doi:10.1103/PhysRevLett.114.123004Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C-60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.Additional Authors: Tiggesbaumker, J.;Meiwes-Broer, K. H.;Lemell, C.;Burgdorfer, J.;Levine, R. D.;Remacle, F.;Kling, M. F