In this work, we analyze the correlation between harmonic generation and multiphoton ionization produced by the mixing of the fundamental and second harmonic of a picosecond Nd-YAG laser in different gases. Particularly, the harmonic conversion efficiency and the rate of ionization are recorded by a self-correlation technique where the fundamental field has variable delay with respect to the second harmonic. We show that the ion and harmonic signals exhibit the same behavior versus the relative delay of both fields. It seems to suggest, at least in our conditions, a positive influence of ionization on the harmonic conversion efficiency. The solution of the propagation equation, which includes electron-ion scattering as the elementary process of harmonic generation, gives a good description of the experimental results.
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