الفهرس 
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Abstract
This work based on a modification of a previously developed model by Mahmoud and Gamal (1995) which is carried out to investigate the physical processes in lithium plasma formed by resonantly laser excitation. The model contains a large number of rate equations for the excited states densities as well as molecular and atomic ions. The computational model consists of a set of rate equations which describe the time dependent Electron Energy Distribution Function (EEDF) and the time evolution of the excited states as well as the atomic and molecular ions densities formed during the interaction of laser excited lithium vapor at the first resonance transition from (2s-2p) under the experimental conditions of (Skenderovic et al, 2000). In which a pulsed laser with an output energy of single pulse 2 mJ with 0.2 cm-1 line width, pulse duration equal to 20 nsec, lithium vapor density varied from 1014 to 1016 cm-3, wave length and laser power density varied from 104 to 105 W.cm-2 to study their effect on EEDF, electrons density, excited states densities, atomic and molecular ions densities. We take into account all atoms, electron and photo interactions namely Associative ionization, induced Associative ionization, Penning ionization, induced Penning ionization, single and two photon ionization, energy pooling collisions, super elastic collisions, excitation, three body recombination, radiative recombination and electron impact ionization. To investigate the behavior of each physical process during the plasma generation, the temporal evolution of each of the excited states as well as the electron density are calculated and discussed in order to analyze the contribution of each of these processes on the population and depopulation of these states. from these computations we concluded that, electrons are mainly generated by photo ionization, induced Penning ionization and induced Associative ionization processes and continued to grow through Associative ionization, electron impact ionization and Penning ionization. The energy pooling plays an important role in populating the highly excited states specially 3p and 3d. Super elastic collision are the mechanisms which are responsible for the electron energy gain, through which, hot electrons can be created in the plasma with energies up to 3.75 eV. Electron impact collisional processes are responsible for the de-population of the highly excited states by electrons gaining their energies through super elastic collisional processes. Also the results show a nonlinear behavior of the energy spectra of the electrons created during the interaction of the laser with lithium vapor. The nonlinear behavior results from superelastic collisions between the free electrons produced by collisional ionization and photoionization with excited states. The results show that a competition exists between the collisional ionization and photoionization processes in producing atomic ions and single photo ionization is the most effective process in producing atomic ions. Also we investigated that resonance ionization process can create a fully ionized plasma of lithium vapor using few nano seconds of laser pulse.