Light emission from microwave discharges in liquid hydrocarbons at the initial stages of their development

Abstract Time‐resolved optical techniques (spectrograph, high‐speed camera, photodiode) were used for scrutinizing the initial stages of the microwave discharge (2.45 GHz, 200–500 W) achieved in liquid alkanes (C n H 2 n + 2 ). Petroleum solvent Nefras S2 80/120 (a mixture of light hydrocarbons with boiling temperatures ranging between 33°C and 205°C) was considered to be representative of alkanes. The discharge was ignited in the liquid, at the end of a molybdenum antenna located under ambient conditions above the liquid. The discharge displaced sequences of light pulses of different shapes and amplitudes, randomly distributed in time. The minimum pulse duration is 0.5 ms. At times close to 1 ms, the spectrum comprises emission bands of the C 2 molecule, lines of hydrogen, and the C + ion, but there is no continuum associated with the emission of the formed solid carbon‐containing particles. In a number of cases, an anomalous spectrum of the C 2 molecule was recorded, with no such sequences having been observed before.