Fig. 15.

a Optical emission spectroscopy results for a APPJ with (red line) and without (black line) DI water at an applied voltage of 2.3 kV. b Metastable Ar emission intensities at 912 nm (red-star line and orange-circle line) and 696 nm (blue-square line and purple-triangle line) with and without DI water as a function of the applied voltage. c O I (777 nm) emission intensities with (red-circle line) and without (black-square line) DI water versus the applied voltage [111]