Fast and ultrafast processes of propane plasma rise and relaxation under excitation by nano- and femtosecond laser pulses at atmospheric pressure were studied. The characteristic relaxation times of the excited states of the propane dissociation products in laser-induced plasma were determined. Mechanisms of plasma formation and dissociation of propane molecules in plasma upon excitation by high-intensity femtosecond laser pulses at power densities exceeding 1 · 1014 W cm−2 were proposed. © 2025 Elsevier B.V., All rights reserved.