Association reactions in femtosecond laser filaments of hexane studied by time-of-flight mass spectrometry with velocity screening

Femtosecond laser filament-induced reactions in gaseous hexane (C₆H₁₄) are studied by time-of-flight ion mass spectrometry. The neutral products are unambiguously distinguished from species produced by ionization for mass analysis, through velocity screening along the flight tube. In addition to hydrogen-capped polyynes, C_<i>n</i>H₂ (<i>n</i> = 4, 6, 8, 10 and 12), the mass spectrometry reveals hydrocarbon molecules in the mass range of <i>m/z</i> 50-146 that have eluded identification in previous studies. The product distributions, together with their dependence on laser pulse energy and repetition rate, provide insight into the association reaction pathways to hydrogen-capped polyynes and other products by laser filaments.