Supersonic jet multiphoton ionization mass spectrometry using nanosecond and femtosecond pulse lasers

The chemical species produced as a result of the thermal decomposition of polystyrene are multiphoton ionized by 500 fs and 15 ns laser pulses. Femtosecond laser ionization gave a more structured mass spectrum and a higher ionization efficiency. This is likely due to the fact that ionization occurs faster than intramolecular relaxation, e.g. photodecomposition, under femtosecond laser pulses.