Nuclear Matter in Intense Magnetic Field and Weak Processes

We study the effect of magnetic field on the dominant neutrino emission processes in neutron stars.The processes are first calculated for the case when the magnetic field does not exceed the critical value to confine electrons to the lowest Landau state.We then consider the more important case of intense magnetic field to evaluate the direct URCA and the neutronisation processes. In order to estimate the effect we derive the composition of cold nuclear matter at high densities and in beta equilibrium, a situation appropriate for neutron stars. The hadronic interactions are incorporated through the exchange of scalar and vector mesons in the frame work of relativistic mean field theory. In addition the effects of anomalous magnetic moments of nucleons are also considered.Comment: 29 pages (LaTeX) including 7 figure

Electrical Conductivity at the Core of a Magnetar

An expression for the electrical conductivity at the core of a magnetar is derived using Boltzmann kinetic equation with the relaxation time approximation. The rates for the relevant scattering processes, e.g., electron-electron and electron-proton are evaluated in presence of strong quantizing magnetic fields using tree level diagrams. It is found that in presence of a strong quantizing magnetic field, electrical conductivity behaves like a second rank tensor. However, if the zeroth Landau levels are only occupied by the charged particles, it again behaves like a scaler of a one dimensional system.Comment: REVTEX File, 4 .eps figures (included

Bulk Viscosity of Magnetized Neutron Star Matter

We study the effect of magnetic field on the bulk viscosity of nuclear matter in neutron stars. We employ the framework of relativistic mean field theory to observe the dense nuclear matter in neutron stars. The effects are first studied for the case when the magnetic field does not exceed the critical value to confine the electrons to the lowest Landau levels. We then consider the case of intense magnetic field to evaluate viscosity for the URCA processes and show that the inequality $p_{F}(e)+p_{F}(p)\geq p_{F}(n)$ is no longer required to be satisfied for the URCA processes to proceed.Comment: Latex 2e file with four postscripts figure

Neutrino opacity in magnetised hot and dense nuclear matter

We study the neutrino interaction rates in hot matter at high densities in the presence of uniform magnetic field. The neutrino cross-sections involving both the charged current absorption and neutral current scattering reactions on baryons and leptons have been considered. We have in particular considered the interesting case when the magnetic field is strong enough to completely polarise the protons and electrons in supernovae and neutron stars. The opacity in such a situation is considerably modified and the cross-section develops anisotropy. This has implications for phenomenon invoked in the literature to explain the observed pulsar kicks.Comment: 22 latex pages and 7 postscript figure

Partial Ionization Cross Sections of Tungsten Hexafluoride Due to Electron Impact

The ionization data of a neutral molecule are crucial to model the energy deposition and dissociative ionization process. We study theoretically the electron impact ionization process and report on the dissociative ionization cross sections of the tungsten hexafluoride cations invoking the modified-binary-encounter-Bethe model. In this model, the binary-encounter-Bethe model is modified by applying the transformation to the binding energies of the molecular orbitals and then normalizing the partial ionization cross sections of the cations using the branching ratios. The normalization is performed at a particular energy and ensures that the branching ratios of different fragments are summed to unity. The model yielded satisfactory results for both the singly and doubly ionized ions. The approach validates the results of Basner et al. The advantages and limitations of this model are also discussed. This work corroborates the importance of mass spectrometry data in the proper understanding of the ionization process

Electron impact partial ionization cross sections of methyl alcohol up to 5 keV using the mass spectrometry data

The electron impact partial ionization cross sections (PICSs) of methyl alcohol fragments are reported from ionization threshold to 5 keV. The calculations employ use of electron impact mass spectrometry data and a modified form of binary-encounter-Bethe (BEB) model. In the modified-BEB approach, the binding energy of each occupied molecular orbital is incremented by an amount such that the highest occupied molecular orbital reflects the appearance potential of a particular fragment. The PICSs are then obtained by appropriately scaling the cross section data using the branching ratios (BR). The BRs can either be obtained from the cross section data or using the mass spectrometry data at an energy at which the mass spectrum is recorded. The PICSs are summed to obtain the total ionization cross sections (TICS) of the methyl alcohol. The results are in good agreement with the experimental results and are superior to the existing theoretical results. A simple approach like this in conjunction with mass spectrometry would be of immense help in modeling and interpretation of ionization data. The study reveals the need for more consistent ion energetics and mass spectrometry data for an accurate modeling of PICSs

Electron impact partial ionization cross sections of 1-butanol

The 1-butanol molecule is one of the most promising sources of biofuel, having the potential to replace fossil fuels. It can be used in combustion engines as fuel. During the combustion, plasma is created in which the electron interactions with neutral targets result in the formation of cations via dissociative ionization process. The energy-dependent cross sections are reported for different cations up to 5 keV in a very simple and efficient way within the framework of the binary-encounter model. The computation approach requires the binary-encounter-Bethe input parameters, ion energetics, and electron ionization mass spectrometry data. A good agreement is observed between the computed cross sections and experimental measurements for various cations. The work emphasizes the role of electron mass spectrometry in the study of the ionization process. The electron collision data would be useful to model the combustion process to develop efficient combustion engines. The present work provides the only available theoretical results for 1-butanol over an extensive energy range

Electron-impact cross sections of acetylene up to 5 keV

The electron impact cross sections like elastic, dissociative ionization, and the total are computed for acetylene from ionization threshold up to 5 keV. The dissociative partial ionization cross sections of various cations are reported using the binary-encounter-Bethe (BEB) model. The elastic cross sections are calculated within molecular framework modified by invoking the single-centre expansion formalism. The total cross sections at these energies are estimated by summing the ionization and elastic cross sections incoherently. The cross sections obtained for different processes are in high degree of convergence with the experimental and theoretical data. The work underlines the role of mass spectrometry data in the study of ionization process as well as the diverse nature of BEB model

Mass Spectrometry-Based Approach to Compute Electron-Impact Partial Ionization Cross-Sections of Methane, Water and Nitromethane from Threshold to 5 keV

The electron impact partial ionization cross-sections of molecules such as methane, water and nitromethane are computed using a modified form of the binary encounter Bethe (BEB) formula. The modified form of the BEB model works on rescaling the molecular binding energies of the orbitals and the scaling of cross-sections using the electron ionization mass spectrometry data. The computed partial ionization cross-sections are consistent with the recommended data and are better than several experimental and theoretical results. The summed partial ionization cross-sections of different fragments also agree with the total ionization cross-sections obtained from BEB and the experimental data. This work highlights the utility of mass spectrometry in the modeling and interpretation of the ionization cross-section data. The limitations and the advantages of the modified form of the BEB model are also discussed