Tunneling through Color Glass Condensate and True Black Disks

We discover new vacuum solutions of the JIMWLK equation, which correspond to center of a gauge group. We improve the color glass condensate (CGC) model by an explicit usage of a density matrix. Studying scattering of CGC states in an external color field, we observe that an amplitude is naturally expressed via group characters. We construct an example that shows how new thin effects may be potentially observed in peripheral collisions. We prove that at any parton density a gluonic CGC state does not become a true black disk. We find a wave function of a true black disk and show that it necessarily contains many quarks. This result corresponds to the necessity of nonvacuum Reggeon loops in a formation of a true black disk.Comment: 13 pages, 2 figures, revtex; final version, improved styl

Capturing Unstable Metallofullerenes

Metallofullerenes are interesting molecules with unique structures and physicochemical properties. After they are formed in the arc-discharge process, they are first buried in the carbon soot, which requires solvent extraction to fish them out, normally followed by HPLC separation. In this minireview, we summarize the main procedures developed to obtain pure metallofullerenes, including well-established extraction with conventional fullerene solvents followed by HPLC (procedure (I) as well as several methods developed for isolation and purification of unstable fullerenes insoluble in conventional fullerene solvents, including chemical modification followed by dissolution (II.1), chemical functionalization during extraction followed by HPLC (II.2), and chemical functionalization of ionic EMFs after redox-extraction followed by HPLC (procedure II.3). The main focus here is on procedure II.3, for which the current status and future perspective are discussed

Sc3CH@C80: selective 13C enrichment of the central carbon atom

Sc3CH@C80 is synthesized and characterized by 1H, 13C, and 45Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. 13C satellites in the 1H NMR spectrum enabled indirect determination of the 13C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the 13C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage 13C distribution in mechanistic studies employing either 13CH4 or 13C powder to enrich Sc3CH@C80 with 13C

Self-assembly of endohedral metallofullerenes: A decisive role of cooling gas and metal-carbon bonding

The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc–C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-Td and Ti@C30-C2v(3)

On the Preparation and Spectroelectrochemical Characterization of Certain 2,5-Bis(het)aryl Substituted Thiophenes

In this work, a series of novel 2,5-bis(het)aryl and 2,5-bis-thienyl substituted thiophenes have been synthesized and characterized by ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and fluorescence spectroscopy as well as cyclic voltammetry. From the electron paramagnetic resonance (EPR)/UV-Vis-NIR spectroelectrochemical data, information about the optical and magnetic properties of the charged species of these compounds have been provided. The spin distributions in the electrochemically generated radical ions were estimated experimentally and compared with theoretical data

On the Electrochemical Reduction of 4-(Thiazol-2-ylazo)-Substituted 1-Chloronaphthalenes: Formation and Characterization of Stable Radical Anions

The electrochemical reduction of two chloro-substituted 4-(thiazol-2-ylazo)has been studied by means of spectroelectrochemistry and simulated with the DFT method. Whereas the 1-chloro-4-(4-chlorothiazol-2-ylazo)forms both a stable radical anion and a dianion, the dianion of 1-chloro-4-(thiazol-2-ylazo)is instable. In the radical anion of both compounds, the spin densities are high not only at the azo moiety but also at C3 in the naphthalene and at C5 in the thiazole moiety. This is in agreement with former experimental results demonstrating the remarkable reactivity of these positions towards thiols which can act as nucleophiles as well as electron donors. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Invariant color calculus and generalized Balitsky-Kovchegov hierarchy

We derive generalization of the Balitsky-Kovchegov (BK) equation for a dipole, which consists of a parton and an antiparton of arbitrary charge. At first, we develop one method of indexless transformation of color expressions. The method is based on an evaluation of the Casimir operator on a tensor product. From the JIMWLK equation we derive the evolution equation for a single parton and prove gluon Reggeization in an arbitrary color channel. We show that there is a color duplication of such Regge poles. Higher t-channel color exchange has its own Regge pole, which residue is proportional to the quadratic Casimir. Taking a fundamental representation, we derive the usual BK equation and shed new light on the meaning of linear and nonlinear terms. Finally, we discuss a linearized version of the generalized BK equation.Comment: 10 pages, 1 figure; final version, improved English, slyle correction

Topological Signatures in the Electronic Structure of Graphene Spirals

Topology is familiar mostly from mathematics, but also natural sciences have found its concepts useful. Those concepts have been used to explain several natural phenomena in biology and physics, and they are particularly relevant for the electronic structure description of topological insulators and graphene systems. Here, we introduce topologically distinct graphene forms - graphene spirals - and employ density-functional theory to investigate their geometric and electronic properties. We found that the spiral topology gives rise to an intrinsic Rashba spin-orbit splitting. Through a Hamiltonian constrained by space curvature, graphene spirals have topologically protected states due to time-reversal symmetry. In addition, we argue that the synthesis of such graphene spirals is feasible and can be achieved through advanced bottom-up experimental routes that we indicate in this work