Time of flight mass spectrometry of polyyne formation in the irradiation of liquid alkanes with femtosecond laser pulses

The production of polyyne molecules arising from the irradiation of liquid octane with femtosecond (fs) laser pulses has been studied using time of flight mass spectrometry (TOFMS). We attribute the primary formation mechanism for polyynes in solution to the creation of small polyyne and cumulene molecules formed in molecular dissociative ionization, that subsequently increase in length through addition reactions with other products C, C2, C2H, the ions of which are detected in the TOFMS of octane. Polyynes up to C14H2 have been identified and we propose that photo-dissociation limits the length of polyynes produced in solution.