Investigation of the fragmentation of explosives by femtosecond laser mass spectrometry

Abstract

We use femtosecond laser mass spectrometry (FLMS) to study the fragmentation patterns of solid phase explosive materials subjected to femtosecond laser pulse irradiation. In condensed phase FLMS a compound deposited on a solid substrate is desorbed into vacuum by femtosecond irradiation forming a plume of ionized and neutral species. Positive or negative ions are accelerated by an electric potential, allowed to drift in the field-free region of a time-of-flight (TOF) mass spectrometry instrument, and flight-times are recorded by a micro-channel plate detector and a digital oscilloscope. From the value of the accelerating field and the ion flight time, the mass-to-charge ratio of each ion is obtained. In this paper we report femtosecond laser mass spectra for the positive and negative ions formed by desorbing TNT and RDX with 150 fs pulses centered at 800 nm. The fragmentation pathways for the formation of the observed ions are described and are used to interpret femtosecond laser induced breakdown spectroscopy results.