000  03732nam a2200253Ia 4500  

003  INBaIIA  
005  20211111120622.0  
008  211028s9999 xx 000 0 eng d  
040  _cIIA Library  
080 
_a043:52 _bMAJ 

100 
_aMajumder,Sonjoy _926317 _eAuthor 

245  0 
_aStudy of atomic and molecular many body processes in astrophysics _ba thesis submitted for the degree of Doctor of Philosophy in Bangalore University, Bangalore _cSonjoy Majumder _h[Ph.D Thesis] 

260 
_aBangalore _bIndian Institute of Astrophysics _c2001 

300  _axvi, 134p.  
500  _aThesis Supervisor B. P. Das  
502 
_bDoctor of Philosophy _cBangalore University , Bangalore _d2001 

520  _aAtomic and molecular processes in astronomical objects have profound implications. Many of those objects in which certain atomic and molecular species have been detected are the sites for evolution of stellar envelopes and star formations. Measurements of atomic and molecular line intensities are powerful diagnostic tools for the exploration of many astrophysical processes. Accurate calculations of energy levels, lifetimes of states, oscillator strengths and shapes of the atomic and molecular transition lines are often necessary to understand those processes. Rigorous treatments of atomic and molecular manybody effects are necessary for accurate calculations of these quantities. Such calculations have become important with the advent of high resolution spectrographs used in several ongoing missions for solar and stellar projects. Even improved experimental data are not adequate for them. Forbidden lines, which is one of the important features in this thesis work, are difficult to measure. Here we have employed various manybody approaches to calculate electronic properties of some atoms, ions and molecules which have astrophysical importance. Both nonrelativistic and relativistic studies have been performed using perturbative and nonperturbative approaches. Effective valence shell Hamiltonian (HV) theory, one of the most advanced nonrelativistic approaches to multireference manybody perturbation theory (MBPT) is used to calculate binding energies (energy relative to first ionization threshold), excitation energies, oscillator strengths and transition probabilities of neutral carbon and calcium. The same method is used for calculating ground state energy difference between the cyclic and linear isomers of propynlidyne (C3H), as well as their harmonic vibrational frequencies, ionization potentials, electron affinities, excited state energies, dipole moments and oscillator strengths, some of which have not been reported before. One of the most important forbidden transitions, magnetic quadrupole transitions for Belike ions are calculated using the multiconfiguration DiracFock met.hod, which is a self consistent variational relativistic manybody method. The leading relativistic correction to the Coulomb interaction known as the Breit interaction is included in these calculations using firstorder perturbation theory. The \v('ak allowed transitions of Mg II are accurately computed using one of the most powerful nonperturbative sizeextensive approaches, the coupled cluster (CC) method. A new approach to generate the DiracFock (DF) orbitals using finite basis set expansions is developed. These DF orbitals are used in the CC calculations to achieve high accuracies for various electronic properties of atoms.  
650 
_aAstrophysics _9794 

650 
_aAtomic Properties _926318 

650 
_aAtomic Systems _919508 

700 
_aB. P. Das _eSupervisor _948865 

856 
_uhttp://prints.iiap.res.in/handle/2248/118 _yClick Here to Access eThesis 

942 
_cTD _2udc 

999 
_c14715 _d14715 