Numerical Investigation of the Tri-Atomic Ions Formation during Laser Ionization Based on Resonance Saturation

Abstract

We present a theoretical investigation of plasma generation in sodium vapor induced by laser radiation tuned to the first resonance line (3S-3P) at λ = 589 ns. A set of rate equations that describe the rate of change of the ground and excited states population as well as the temporal variation of the electron energy distribution function (EEDF), beside the formed atomic ion Na + , molecular ion + 2 Na and tri-atomic ions + 3 Na are solved numerically. The calculations are carried out at different laser energy and different sodium atomic vapor densities under the experimental conditions of Tapalian and Smith (1993) to test the existence of the formed tri-atomic ions. The numerical calculations of the electron energy distribution function (EEDF) show that a deviation from the Maxwellian distribution due to the super elastic collisions effect. In addition to the competition between associative ionization (3P-3P), associative ionization (3P-3D) and Molnar-Hornbeck ionization processes for producing + 2 Na , the calculations have also shown that the atomic ions Na + are formed through the Penning ionization and photoionization processes. These results are found to be consistent with the experimental observations.

Impact of Initial Electron Development on Sodium Plasma Generation Using LIBORS Technique: Numerical Modeling

“…[29]. Then, this model is modified [30] and could successfully investigate the finding of the experimental observation given in [1] that carried out to measure to the first time the formation of tri-atomic ions in laser ionization of sodium vapor. As an extension to this work, the present study examines the ionization of sodium vapor irradiated by CW laser radiation taken into account the occurrence of various seed electron generation processes.…”

“…This is a property of the alkali metal elements. Here, we recall that the modified LIBORS model [30] is applied to analyze plasma formation induced by pulsed laser radiation. The sodium atom is presumed to comprising 22 levels namely; a ground state, 18 excited states and three ionic states (atomic, molecular, and tri-atomic).…”

“…The above mentioned physical processes are encountered in the applied model given in Ref. 30 This model solves iteratively a set of rate equations that represent the time variation of the instantaneous population density of the various species present in the formed plasma. Besides, the model solves the Boltzmann equation for the electron energy distribution for the given normalization conditions.…”