Anomalous behaviour of the non-selective ionisation signal pulse under laser ablation into a flame

When applying to the probing electrode the potentials with the different polarity one can notice that the non-selective and selective signals behave quite differently. In case of the positive potential compared with the negative one the non-selective signal shows anomalous behavior: it changes the shape and polarity and its amplitude increases dramatically while the selective one only changes the polarity that can be explained by the electrical properties of the flame reaction zone, which effectively eliminates the charges from laser plasma by the recombination.