Emission spectra and gas products of microwave discharge in liquid n‐heptane with and without argon bubbling (6–40 l h−1) are investigated. The discharge was excited in a system with a coaxial input of energy. The pressure above the surface of the liquid was equal to atmospheric pressure. It is shown that the addition of argon changes the spectral composition of the plasma radiation, in which the emission of hydrogen and argon atomic lines appears. The addition of argon does not affect the rotational and vibrational temperatures of the state C2true(d3normalΠgtrue), the composition and the ratio of the main gas products (H2, CH4, C2H2, C2H4).

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Carbon‐containing nanosize solid‐state phase have been produced in the atmospheric pressure microwave (MW) plasma ignited in the gas bubbles in liquid alkanes CnH2n+2 (n = 7, 8, 10, 15, 16). Gas bubbles are generated by flow of argon. According to SEM data, the solid‐state products are represented by particles having dimensions in the range of 100–200 nm. Raman spectra of the sooty‐like unpurified solid products permit to categorize them as sp3+sp2 mixed forms of carbon comprising mainly an “damaged grapheme” along with a “few‐layer” graphite nanoparticles. NMR spectra of the solid products show strong aromatization and formation of various unsaturated molecular fragments. FTIR‐ATR spectra indicate that the carbonaceous nanoparticles are contaminated with minor amounts of different hydrocarbon residues and oxidized species.