Spectroscopy of Microwave Discharge in Liquid C7–C16 Hydrocarbons

Emission spectra of in-liquid microwave plasma in C7–C16 hydrocarbons were studied in the range of wavelengths from $200$ to $800$ nm. It was shown that spectra are similar for all studied hydrocarbons. Swan-bands only were observed in the plasma emission. Model of Swan-bands emission was designed for experimental spectra processing. Rotational and vibrational temperatures determined from sequences with $v = –1$, $0$, $+1$ of $\text{C}_2$-bands were $1600 \pm 200$ K and $7000 \pm 2000$ K correspondingly. Addition of $\text{Ar}$ in the plasma decreased the rotational up to $700$ K but did not change the vibrational temperature. It was shown that studied in-liquid microwave plasma is non-equilibrium. Results of electrodynamic modeling of microwave discharge apparatus and some information on the solid phase generated in hydrocarbon plasma processing were presented.