Search for the Chiral Magnetic Effect in Au+Au collisions at sNN=27\sqrt{s_{_{\rm{NN}}}}=27 GeV with the STAR forward Event Plane Detectors

A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}}=27$ GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity $|\eta|<1.0$ and at forward rapidity $2.1 < |\eta|<5.1$. We compare the results based on the directed flow plane ($\Psi_1$) at forward rapidity and the elliptic flow plane ($\Psi_2$) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to $\Psi_1$ than to $\Psi_2$, while a flow driven background scenario would lead to a consistent result for both event planes[1,2]. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.Comment: main: 8 pages, 5 figures; supplementary material: 2 pages, 1 figur

Variational transition state theory. Progress report, July 1, 1981-June 30, 1982

Further development of variational transition-state theory was carried out during this period and several applications made for many atom-molecule, bimolecular, and muonium reactions. Only qualitative results are reported. (DLC

Variational transition state theory

In recent years our research group has made a systematic effort to study the validity of transition state theory (TST). We have found that the conventional theory is sometimes remarkably accurate, but in many other cases it leads to large errors. Fortunately we have found that a much more reliable theory that has many of the advantages of conventional TST can also be formulated, and it can be applied to practical problems with an effort that is much closer to that required for conventional transition state theory than to that required for quantal dynamics calculations. The two most important features in the improved approach to transition state theory state theory are the variational determination of the transition state and the incorporation of tunneling contributions by multidimensional semiclassical approximations. 13 refs

Adsorbate-induced changes in magnetic interactions in Fe₂(dobdc) with adsorbed hydrocarbon molecules

International audienc

Calculation of converged rovibrational energies and partition function for methane using vibrational-rotational configuration interaction

The rovibration partition function of CH4 was calculated in the temperature range of 100-1000 K using well-converged energy levels that were calculated by vibrational-rotational configuration interaction using the Watson Hamiltonian for total angular momenta J=0-50 and the MULTIMODE computer program. The configuration state functions are products of ground-state occupied and virtual modals obtained using the vibrational self-consistent field method. The Gilbert and Jordan potential energy surface was used for the calculations. The resulting partition function was used to test the harmonic oscillator approximation and the separable-rotation approximation. The harmonic oscillator, rigid-rotator approximation is in error by a factor of 2.3 at 300 K, but we also propose a separable-rotation approximation that is accurate within 2% from 100 to 1000 K. (C) 2004 American Institute of Physics

Alkylation and transalkylation reactions of aromatics

A symposium. D. functional theory calcns. were carried out to analyze the reaction energy of solid-state acid-catalyzed Me-transfer reactions. Different mechanistic routes for the alkylation of C6H6 and PhMe by MeOH were compared. An associative reaction path via an intermediate complex of MeoH and the substrate is the preferred route. The activation energy is 123 and .apprx.120 kJ/mol for C6H6 and PhMe, resp. A MeO-mediated path involves very high activation barriers compared to the associative route. However, coadsorbed H2O gives a large redn. of the activation energy for this reaction. Different mechanisms for PhMe transalkylation, involving Ph2CH2 as an intermediate, directly via Me transfer, and MeO-mediated, were compared. For the 1st mechanism, the preferred route is that where the reaction chain of elementary reactions is propagated via H- transfer. The rate-detg. step is the initial dehydrogenation, with an activation energy of +277 kJ/mol, which is present only in the very 1st step of the reaction chain. In the following steps, the initial dehydrogenation is replaced by proton-assisted cracking of Ph2CH2 as the step with the highest activation barrier. The direct mechanisms via Me transfer or via intermediate MeO do present activation barriers that are lower than the dehydrogenation step but higher than via Ph2CH2/H- transfer-mediated reaction. For small-pore zeolites, where large mols. like Ph2CH2 cannot be formed, they should be considered as optional routes for the transalkylation reactio