Investigation of silicon oxide emission spectra observed in a pulsed discharge and a laser-induced plasma

Emission spectra of silicon oxide molecules in the spectral range from 228 to 246 nm have been observed in a pulsed discharge and a laser-produced plasma. The vibrational bands belonging to the Δυ = -1,0, + 1 sequences of the SiO A 1 Π-X 1 Σ + system have been reproduced by computer simulations in order to determine the vibrational and rotational temperatures. In the pulsed discharge, the vibrational temperature has been found to exceed the rotational temperature several-fold, indicating the non-thermal character of this type of plasma. In contrast, similar values of the two temperatures have been deduced for the plasma produced by pulsed-laser ablation, proving a collisional equilibrium. Simple criteria based on intensity ratio measurements are proposed for the temperature evaluation from the SiO emission bands.