Influence of the laser spark generation mechanism on electric and magnetic fields in its vicinity

A laser spark formed by the focused beam of a ns high energy laser in a gas filled interaction chamber can mimic energetic events in the early Earth atmosphere, which are thought to be instrumental in the synthesis of simple chemical compounds, such as some amino acides, [1, 2], which later might have participated in more complex organic syntheses leading to the origin of terrestrial life. Some of these molecules are optically active and it is an experimental fact that the model experiments in the gas-filled chamber yield an unequal ratio of right-handed (R-) and left-handed (L-) optical isomers. It has been conjectured that this asymmetry between the Rand Lspecies is induced by the synthesis going on under the action of superimposed electric and magnetic fields occurring in the spark vicinity as a consequence of its polarization and internal currents. Such fields during an optical breakdown in the air have actually been directly measured, [3]. The orientation of the electric dipole formed in the plasma, which is caused by the polarization due to the plasma radial expansion in the self-generated magnetic field, has the polarity, which very much depends on the disposition of electron density and electron temperature gradients inside the plasma. These gradients depend, in turn, on the mechanism of the laser spark formation. In the literature essentially three different mechanisms can be tracked down: (1) light detonation wave, [4], (2) radiation hydrodynamics supersonic propagation, [5], and (3) delayed breakdown action, also described in [4]. The present contribution is aiming at an assessment of the mentioned spark formation models and their comparaison with the experimental findings.