Broadband Mid-Infrared Measurements for Shock-Induced Chemistry

We are developing methods for measuring transient vibrational spectroscopy during shock loading in order to test and validate reactive molecular dynamic predictions of shock induced chemistry in explosives. Broadband (< 600 to > 2000 cm(-1)) femtosecond mid-infrared spectra have been generated by mixing 400 nm and 800 nm pulses in air. Broadband single shot detection was measured using 1) nonlinear up conversion, which was successful from 700-1300 cm(-1) and offers potential for detection across the entire source spectral range, 2) pyroelectric detection, which was determined to be insufficiently sensitive, and 3) microbolometer based detection, which was successful from 600-1250 cm(-1) as limited by the thermal imaging filter on the detector chip. Initial experiments were performed on shocked nitromethane measuring transient mid-infrared transmission spectra using the microbolometer, but conclusive results have not yet been obtained and further refinements are underway.