The photoionization process generates free electrons which possess enough kinetic energy to dissociate the neutral molecules, like nitrogen molecules and oxygen molecules in air. I want to know the approximate time scale of dissociation process. I thought it is about dozens of microsecond dependent on electron energy. If someone know the time scale of classical electron impact dissociation of molecules, the answer is also welcome.
Since formed plasma atomizes and excites samples and may bring about translational energy of the ion to internal
energy in the ion during collision, it may not be necessary to give it a standard time as within a very small timeframe the plasma expands at supersonic velocities and cools. It is in few seconds but bear in mind that the detection limit varies from one neutral element to the next depending on the specimen type and the experimental apparatus used
Dissociation time ~ 1/(k*Ne), where k is constant of electron impact dissociation reaction and Ne is electron density. Value of k can be found in I.A. Kossyi, A.Yu. Kostinsky, A.A. Matveev, V.P. Silakov, Plasma Sources Sci. Technol. 1 (1992) 207-220
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