Modern Trends In Physics - Proceedings Of The 4th International Conference On Modern Research

Lotfia Mohamed el Nadi

• Publisher: WSPC
• Year: 2013
• Print ISBN: 9789814504881
• eBook ISBN: 9789814504904
• Topic: Biological Sciences
• Subtopic: Science General
• Index: Biological Sciences

The objectives of the conference are to develop greater understanding of physics research and its applications to promote new industries; to innovate knowledge about recent breakthroughs in physics, both the fundamental and technological aspects; to implement of international cooperation in new trends in physics research and to improve the performance of the physics research facilities in Egypt. This proceedings highlights the latest results in the fields of astrophysics, atomic, molecular, condensed matter, laser, nuclear and particle physics. The peer refereed papers collected in this volume were written by international experts in these laser fields.

Contents:

• Atomic, Molecular and Condensed Matter Physics:
  • Solar Activities and Space Weather Hazards (Ahmed A Hady)
  • Electron Beam Ion Trap and Its Applications (Yaming Zou)
  • Fundamental Studies and Applications of Highly Charged Ions (Reinhold Schuch)
  • Stark Broadening Calculations of Several Ti Lines (A I Refaie and H Sharkawy)
  • Synthesis of Rare Earth Doped and Undoped GaN Nano-Crystallites (Lotfia El Nadi, S Ahmed, M Awaad, Magdy Omar and Y Badr)
  • Conductivity Enhancement of Mn-Zn Ferrite by Gamma Irradiation (M A Ahmed, A M Diab and S F Mansour)
  • Giant Enhancement in the Physical Properties of LaFeO 3 by Substitution of Divalent Ions (M A Ahmed, S I Dek, M M Arman)
• High Density Short Pulse Lasers, Lasers and Applications:
  • Advanced Laboratory for High Density Physics (Lotfia El Nadi, A Naser A Fettoh, A Refaie, Galila A Mehena, Hussien A Moniem, Hisham Imam, Khaled A Elsayed, Magdy Omar and Salah H Naby)
  • High Energy Density Physics: The Laser Field of Tomorrow (Richard R Freeman)
  • The Texas Petawatt Laser and Technology Development Towards an Exawatt Laser (Todd Ditmier)
  • XUV and Soft X-ray Laser Radiation from Ni-like Au (Wessameldin S Abdelaziz and H M Hamed)
  • Novel Process for Laser Stain Removal from Archeological Oil Paintings (Lotfia El Nadi, Osama El-Feky, Galila Abdellatif and Sawsan Darwish)
  • Application of Laser Induced Plasma Spectroscopy on Breast Cancer Diagnoses (A Abd-Alfattah, A A Eldakrouri, H Emam and I M Azzouz)
  • Ultrafast Process in Condensed Matter Studied with Ultrashort Laser Pulses (Panagnioti A Loukakous)
• Nuclear, Particle Physics and Astrophysics:
  • Charge Measurements of Fragmented Nuclei of Si at Different Energies (M S EL-Nagdy, A Abdelsalam, A Algaood and M Ahmed)
  • Research Studies Performed Using the Cairo Fourier Diffractometer Facility (R M A Maayouf)
  • K -Surfaces in Schwarzschild Geometry (Ayub Faridi, Fazal-E-Aleem and Haris Rashid)
  • Light-Strange Mesons Decays in the Quark Model (A M Yasser, E M Hassan, M A Fawzy and M A Allosh)
  • Surprising Rapid Collapse of Sirius B from Red Giant to White Dwarf Through Mass Transfer to Sirius A (Shahinaz Yousef and Ola Ali)
  • Evaluation of Radioactivity Concentration in Tilapia Nilotica and Radiation Dose to Egyptian Population (Hannan H Amer and Enas H El-Khawas)
  • Solar Forcings on Nile and Earthquakes (Saad Mohammed Al-Shehri, Ismail Sabbah, Shahinaz Yousef and Magdy Y Amin)
• and other papers

I. ATOMIC, MOLECULAR AND CONDENSED MATTER PHYSICS

I-1 KEYNOTE AND PLENARY PAPERS

Photo-excitation and Photoionization for Plasma Opacities under the Iron Project

Sultana N. Nahar

Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA E-mail: [email protected]

Opacity gives a measure of radiation transport in a medium such that higher or lower opacity indicates more or less attenuation of radiation. As the radiation propagates, opacity is caused by the absorption and emission of radiation by the constituent elements in the medium, such as astrophysical plasmas. It is also affected by photon scatterings. Hence opacity depends mainly on the intrinsic atomic processes, photo-excitation in a bound-bound transition, photoionization in a bound-free transition, and photon-electron scattering. Monochromatic opacity at a particular frequency, κ(ν), is obtained mainly from oscillator strengths (f) and photoionization cross sections (σ_PI). However, the total monochromatic opacity is obtained from summed contributions of all possible transitions from all ionization stages of all elements in the source. Calculation of accurate parameters for such a large number of transitions has been the main problem for obtaining accurate opacities. The overal mean opacity, such as Rosseland mean opacity (κ_R), depends also on the physical conditions, such as temperature and density, elemental abundances and equation of state such as local thermodynaic equilibrium (LTE) of the plasmas. For plasmas under HED (high energy density) conditions, fluid dynamics may be considered for shock waves such as in a supernova explosion.
In this report, I will exemplify the necessity for high precision atomic calculations for the radiative processes of photoexcitation and photoionization in order to resolve some perplexing astrophysical problems relevant to elemental abundances and hence opacities. In particular I will present results on oscillator strengths of Fe XVIII and photoionization cross sections of Fe XVII which are abundant in high temperature plasmas, such as solar corona, and photoionization and recombination of O II which is abundant in low temperature plasmas, such as in a planetary nebula. Sophisticated atomic calculations under the Iron Project are revealing important and dominant features not included in the current opacities. Opacities with these new results are expected to resolve the longstanding problems on abundances in the sun, orion nebula etc.

Keywords: Photoionization; Oscillator strengths; Opacities; Solar and Nebular abundances

1. Introduction

Opacity is a fundamental quantity for studying various quantities such as elemental abundances, physical conditions, stellar pulsations etc of astrophysical and laboratory plasmas. It is used in astrophysical models to obtain internal structure, chemical composition, evolution of states, such as, in local thermodynamic equilibrium (LTE) of the plasmas, etc. As the radiation propagates, it looses energy and slows down by absorption and emission by the constituent elements. The resultant effect is the opacity. Because of opacity the high energy gamma radiation produced by the nuclear fusion in the core of the sun takes over a million years to travel to the surface and escape as optical or low energy photons. Opacity depends on the atomic process of photo-excitations, photoionization and photon scattering.

However, calculation of opacity is quite involved as described in the theory section. For the photon-ion interactions, it depends on the oscillator strengths and photoionization cross sections. Consideration of these processes require large amount of atomic data for all possible radiative transitions. Currently available atomic data for all ions are not accurate and complete enough to compute accurate opacities for various astrophysical problems.

1.1. The Opacity Project and the Iron Project

Prior to the Opacity Project (OP),^1,2 there were large discrepancies between astrophysical observations and theoretical predictions obtained using existing opacities for plasmas. These opacities were calculated mainly by Los Alamos National Lab (LANL) using the atomic data obtained from simple approximations. Los Alamos opacities were incorrect by factors of 2 to 5 resulting in inaccurate stellar models. These could not model the Cepheid stars, important to determine distances in astronomy. In response to a plea³ for accurate opacity from accurate atomic parameters initiated the Opacity Project, an international collaboration of about 25 scientists from 6 countries

Under the OP the first systematic and detailed studies were carried out for the radiative processes of photoexcitation and photoionization for all astrophysically abundant atoms and ions from hydrogen to iron. Computations were carried out in ab initio close coupling approximation and using R-matrix method. Large amount of atomic data for energy levels, oscillator strengths and photoionization cross sections were obtained. The atomic data are available at data base TOPbase⁴ at CDS. New features in photoionization cross sections were revealed. The data were used to calculate the monochromatic opacities and Rosseland mean opacities. The long standing problem on the pulsation ratios of cepheid variables were solved. These atomic data have continued to solve many astrophysical problems. However, a large part of the data are not precise enough for various diagnostics and astrophysical problems.

A follow-up of the OP, the international collaboration of the Iron Project (IP)⁵ was initiated to focus on both the radiative ...

Table of contents

• Cover
• Title Page
• Copyright
• Contents
• Foreword
• Introduction
• Conference Photos
• Opening Honorary Keynote Presentation
• The Variation of the Solar Diameter and Irradiance: Eclipse Observation of July 11, 2010
• I. Atomic, Molecular and Condensed Matter Physics
• II. High Density Short Pulse Lasers, Lasers and Applications
• III. Nuclear, Particle Physics and Astrophysics
• Author Index