• Energy Research

We discuss the dependence of transverse energy production on projectile mass, target mass, and on the impact parameter of the heavy ion reaction. The transverse energy is shown to scale with the number of participating nucleons. Various methods to estimate the attained energy density from the observed transverse energy are discussed. It is shown that the systematics of the energy density estimates suggest average of 2-3 GeV/fm/sup 3/ rather than the much higher values attained by assuming Landau-stopping initial conditions. Based on the observed scaling of the transverse energy, an initial energy density profile may be estimated. 11 refs., 4 figs.

Copyright (2016) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Li, W., & Ma, A. (2016). Reaction mechanism and reaction coordinates from the viewpoint of energy flow. The Journal of chemical physics, 144(11), 114103 and may be found at http://dx.doi.org/10.1063/1.4943581. ; Reaction coordinates are of central importance for correct understanding of reaction dynamics in complex systems, but their counter-intuitive nature made it a daunting challenge to identify them. Starting from an energetic view of a reaction process as stochastic energyflows biased towards preferred channels, which we deemed the reaction coordinates, we developed a rigorous scheme for decomposing energy changes of a system, both potential and kinetic, into pairwise components. The pairwise energyflows between different coordinates provide a concrete statistical mechanical language for depicting reaction mechanisms. Application of this scheme to the C7eq → C7ax transition of the alanine dipeptide in vacuum revealed novel and intriguing mechanisms that eluded previous investigations of this well studied prototype system for biomolecular conformational dynamics. Using a cost function developed from the energy decomposition components by proper averaging over the transition path ensemble, we were able to identify signatures of the reaction coordinates of this system without requiring any input from human intuition. ; Funding support from the National Institutes of Health (No. R01 GM086536) is acknowledged.

Atom-mapped SMILES, barrier heights, reaction energies, and Reaction Mechanism Generator (RMG) reaction template for 1143 radical reactions are listed in the comma separated value files wb97xd3_rad.csv and ccsdtf12_rad.csv. These data can be used to augment the previously published RDB7 dataset. Q-Chem output files for the geometry optimizations and harmonic vibrational analysis are provided at the ωB97X-D3/def2-TZVP level of theory and stored in wb97xd3_rad.tar.gz. All output files for the reactant and transition state, as well as many output files for the products, directly come from Grambow's repository at 10.5281/zenodo.3731554 and are provided here simply for convenience. However, similar to Spiekermann's 10.5281/zenodo.6618262, new DFT calculations for some of the products are included here. Since all reactions with multiple products from Grambow's 10.5281/zenodo.3731554 contained one Van Der Waals complex, this repository separates the product complexes into individual product geometries and recalculates the geometry optimization and vibrational frequency at ωB97X-D3/def2-TZVP. The numbering of reaction indices matches that from Grambow's repository to facilitate easy comparison. Molpro output files from the single-point energy calculations are provided at the CCSD(T)-F12/cc-pVDZ-F12 level of theory for each species optimized using ωB97X-D3/def2-TZVP. These results are stored in ccsdtf12_rad.tar.gz. The single-point energies are also calculated using UCCSD(T)-F12/cc-pVDZ-F12 for two reactions and are stored in uccsdtf12.zip. This subset is only used for a brief validation comparison.

Atom-mapped SMILES, barrier heights, reaction energies, and Reaction Mechanism Generator (RMG) reaction template for 1143 radical reactions are listed in the comma separated value files wb97xd3_rad.csv and ccsdtf12_rad.csv. These data can be used to augment the previously published RDB7 dataset. Q-Chem output files for the geometry optimizations and harmonic vibrational analysis are provided at the ωB97X-D3/def2-TZVP level of theory and stored in wb97xd3_rad.tar.gz. All output files for the reactant and transition state, as well as many output files for the products, directly come from Grambow's repository at 10.5281/zenodo.3731554 and are provided here simply for convenience. However, similar to Spiekermann's 10.5281/zenodo.6618262, new DFT calculations for some of the products are included here. Since all reactions with multiple products from Grambow's 10.5281/zenodo.3731554 contained one Van Der Waals complex, this repository separates the product complexes into individual product geometries and recalculates the geometry optimization and vibrational frequency at ωB97X-D3/def2-TZVP. The numbering of reaction indices matches that from Grambow's repository to facilitate easy comparison. Molpro output files from the single-point energy calculations are provided at the CCSD(T)-F12/cc-pVDZ-F12 level of theory for each species optimized using ωB97X-D3/def2-TZVP. These results are stored in ccsdtf12_rad.tar.gz. The single-point energies are also calculated using UCCSD(T)-F12/cc-pVDZ-F12 for two reactions and are stored in uccsdtf12.zip. This subset is only used for a brief validation comparison. Added InChI strings

Atom-mapped SMILES, barrier heights, reaction energies, and Reaction Mechanism Generator (RMG) reaction template for 1143 radical reactions are listed in the comma separated value files wb97xd3_rad.csv and ccsdtf12_rad.csv. These data can be used to augment the previously published RDB7 dataset. Q-Chem output files for the geometry optimizations and harmonic vibrational analysis are provided at the ωB97X-D3/def2-TZVP level of theory and stored in wb97xd3_rad.tar.gz. All output files for the reactant and transition state, as well as many output files for the products, directly come from Grambow's repository at 10.5281/zenodo.3731554 and are provided here simply for convenience. However, similar to Spiekermann's 10.5281/zenodo.6618262, new DFT calculations for some of the products are included here. Since all reactions with multiple products from Grambow's 10.5281/zenodo.3731554 contained one Van Der Waals complex, this repository separates the product complexes into individual product geometries and recalculates the geometry optimization and vibrational frequency at ωB97X-D3/def2-TZVP. The numbering of reaction indices matches that from Grambow's repository to facilitate easy comparison. Molpro output files from the single-point energy calculations are provided at the CCSD(T)-F12/cc-pVDZ-F12 level of theory for each species optimized using ωB97X-D3/def2-TZVP. These results are stored in ccsdtf12_rad.tar.gz. The single-point energies are also calculated using UCCSD(T)-F12/cc-pVDZ-F12 for two reactions and are stored in uccsdtf12.zip. This subset is only used for a brief validation comparison. Added InChI strings

Neutron capture .gamma.-ray spectroscopy is a powerful technique to study the .gamma.-decay of unbound levels just above the neutron separation energy. It is generally believed that the (n,.gamma.) reaction proceeds by way of a compound nucleus reaction of great complexity; and, therefore, the capture .gamma.-ray spectrum should be describable in terms of statistical laws. However, measurements have shown that effects are present due to single-particle motions and due to giant resonances. The study of (n,.gamma.) spectra averaged over as many resonances as possible provides one of the best experimental means of directly obtaining reliable values for radiative transition probabilities from highly excited nuclear states. In very select cases, unbound levels which are populated in allowed .beta. decay can also be observed as neutron resonances. These ideas are illustrated with examples of recent data.

We discuss the dependence of transverse energy production on projectile mass, target mass, and on the impact parameter of the heavy ion reaction. The transverse energy is shown to scale with the number of participating nucleons. Various methods to estimate the attained energy density from the observed transverse energy are discussed. It is shown that the systematics of the energy density estimates suggest averages of 2--3 GeV/fm{sup 3} rather than the much higher values attained by assuming Landau-stopping initial conditions. Based on the observed scaling of the transverse energy, an initial energy density profile may be estimated. 14 refs., 4 figs.

Recent studies have shown straightforward systematic behavior as a function of constant proton and neutron number for neutron-induced fission cross sections of the actinide elements in the incident-neutron energy range 3 to 5 MeV. In this report, the second in a series, fission cross-section values are studied over the MeV incident-neutron energy range, and at 0.0253 eV. Fission-barrier heights and neutron-binding energies are correlated by constant proton and neutron number; however, these systematic behaviors alone do not explain the trends observed in the fission cross-section values.

Ph.D ; DOCTOR OF PHILOSOPHY (CDE-ENG)

The 1977 Wapstra and Bos nuclear mass data tables were used to derive tables for thresholds and Q values of nuclear reactions induced by neutrons, protons, deuterons, tritons, /sup 3/He ions, alpha particles, and photons. The tables are displayed on microfiche included with the report.