Excitation functions of191+193Ir,197Au(6Li,xn+yp) compound nuclear reactions at ELi=48–156 MeV

Excitation functions of the compound nuclear reactions^191+193Ir,¹⁹⁷Au(⁶Li,xn+yp) forx =3–13 andy=0–2 have been investigated by means of in-beamγ-ray spectroscopy at the 156 MeV⁶Li beam of the Karlsruhe Isochronous Cyclotron. The beam energy has been varied in the range of 48 to 156 MeV in steps of about 10 MeV by Be-absorber foils in the external beam line. Absolute cross sections have been determined by normalizing the measuredγ-ray intensities to the production cross sections ofK- X-rays in the target. The experimental excitation functions are discussed on the basis of predictions of the preequilibrium (hybrid) model. While in most cases the theoretical calculations fairly well reproduce energy position and shapes of the curves, strong discrepancies in the absolute scale of the cross sections are observed. The theoretical predictions overestimate the (⁶Li,xn) cross sections by a factor of about 6. Conspicuous anomalies have been detected when comparing the (⁶Li, xn+1(2)p) reactions with (⁶Li,xn) reactions. The reactions with emission of one or two protons are considerably enhanced. The discrepancies and anomalies observed are tentatively explained by the influence of direct reaction channels as the⁶Li break-up, which experimentally proved to be the dominant contribution to the total reaction cross section. The enhancement of the reactions with emission of protons may be a consequence of transfer reactions into highly excited states combined with compound nucleus formation thus implying a cluster effect in preequilibrium emission process.     

Similarity of Percolation Thresholds on the HCP and FCC Lattices

Extensive Monte Carlo simulations were performed in order to determine the precise values of the critical thresholds for site (p ^hcp _{c, S} =0.199 255 5±0.000 001 0) and bond (p ^hcp _{c, B} =0.120 164 0±0.000 001 0) percolation on the hcp lattice to compare with previous precise measurements on the fcc lattice. Also, exact enumeration of the hcp and fcc lattices was performed and yielded generating functions and series for the zeroth, first, and second moments of both lattices. When these series and the values of p _c are compared to those for the fcc lattice, it is apparent that the site percolation thresholds are different; however, the bond percolation thresholds are equal within error bars, and the series only differ slightly in the higher order terms, suggesting the actual values are very close to each other, if not identical.     

Einstein-Cartan-Maxwell-bianchi type-V cosmological models

Exact cosmological solutions of the Einstein- Cartan-Maxwell equations with spin, stiff matter and an electromagnetic field for Bianchi type-V universes are obtained. A class of nonsingular solutions is presented. The most important characteristic of these solutions is that in one case the effect of the electromagnetic field is to reduce the value of the minimum volume while in another case there exists the possibility of enlarging this value arbitrarily.     

Determination of alignment tensor components for the H(2p) charge exchange excitation in proton-argon collisions

Alignment tensor components 〈T(L) _KQ ⁺ 〉 have been determined for the H(2p) charge exchange excitation in proton-argon collisions at an incident proton energy of 1.5 keV, and scattering angles Θ _s =4.3°, 4.9°, and 6.0°. It is demonstrated that the measured photon angular distribution cannot be described in terms of only λ and ? parameters.     

Inclusive Λ(1,520) production in 100 GeVp Be interactions

The reactionpBe→Λ(1,520)X has been measured at 100 GeV incident momentum in the kinematic range 0.15<x<0.35 \((x = 2p_\parallel ^{c.m} /\sqrt s )\) andP _T <1 GeV. The invariant cross section is compatible with that measured forpp interactions at the CERN-ISR. The differential cross sectiondσ/dp _T ² is fitted to an exponentiale ^?αp _T ² with α=2.7 GeV^?2.     

On the relative stability of states and first-order phase transition in systems far from equilibrium

A method for classifying the states of a macroscopic dissipative system according to their stability with respect to finite-amplitude localized fluctuations and perturbations is presented. Since the method does not rely on a extremum principle it is applicable to open systems far from equilibrium. It appears that in general there exists at most one absolutely stable state (up to symmetry). Simple examples are given for systems without absolutely stable state.     

An exact bianchi type-V tilted cosmological model with matter and an electromagnetic field

We present a cosmological solution of the source-free Einstein-Maxwell equations with stiff matter and an electromagnetic null field, which is a locally rotationally symmetric tilted Bianchi type-V universe.     

Radiation generated by the ultrafast migration of a positive charge following the ionization of a molecular system

Electronic many-body effects alone can be the driving force for an ultrafast migration of a positive charge created upon ionization of molecular systems. Here we show that this purely electronic phenomenon generates a characteristic IR radiation. The situation when the initial ionic wave packet is produced by a sudden removal of an electron is also studied. It is shown that in this case a much stronger UV emission is generated. This emission appears as an ultrafast response of the remaining electrons to the perturbation caused by the sudden ionization and as such is a universal phenomenon to be expected in every multielectron system.     

Inner-shell single and double ionization potentials of aminophenol isomers

A comprehensive study of single and double core ionization potentials of the aminophenol molecule is reported. The role of relaxation, correlation, relativistic, and basis set effects in these potentials is clarified. Special attention is paid to the isomer dependence of the single and double core ionization potentials. Some of them are also compared with the respective values of the phenol and aniline molecules. It is shown that the core level single ionization potentials of the para-, meta-, and ortho-aminophenol molecules differ only slightly from each other, rendering these structural isomers challenging to distinguish for conventional x-ray photoelectron spectroscopy. In contrast, the energy needed to remove two core electrons from different atoms depends noticeably on the mutual arrangement and even on the relative orientations of the hydroxyl and amine groups. Together with the electrostatic repulsion between the two core holes, relaxation effects accompanying double core ionization play a crucial role here. The pronounced sensitivity of the double ionization potentials, therefore, enables a spectroscopic characterization of the electronic structure of aminophenol isomers by means of x-ray two-photon photoelectron spectroscopy.     

Synthesis, crystal structure, and physical properties of BaAg2Cu[VO4]2: a new member of the S = 1/2 triangular lattice

By application of flux growth methods in combination with redox reactions, single crystals of BaAg(2)Cu[VO(4)](2) can be synthesized. A new structure type (triclinic, P1, Z = 2, a = 5.448(2) ?, b = 5.632(3) ?, c = 14.393(6) ?, α = 94.038(9)°, β = 90.347(6)°, and γ = 118.195(5)°) has been found and will be described here. Structure-properties relationships have been investigated by spectroscopic methods (IR, UV-vis-NIR, ESR) and the electronic structure will be discussed within the angular-overlap model (AOM) for Cu(2+). Furthermore, we present the magnetization and specific heat data for BaAg(2)Cu[VO(4)](2) representing a Heisenberg spin system with exclusive super-super exchange (SSE) on a frustrated magnetic triangular lattice. Considerable antiferromagnetic (AFM) low-dimensional interaction is evident, and ferromagnetic-like long-range order sets in at ≈0.7 K.