Generation of nanosecond broadband UV pulses for multiplex nonresonant pump four-wave mixing spectroscopy of OH radicals

The generation of broadband ultraviolet (BBUV) pulses from the second harmonic generation of 7 ns broadband dye laser using two thin BBO crystals of 0.5 mm. The BBUV pulses obtained in the experiment have enough power for the multiplex nonresonant pump four wave mixing (NRP-FWM) spectroscopy of OH radicals in combustion reaction and a wide spectral width enough to cover several Rl and R2 branch electronic transition lines of those chemical species. To measure the spectrum, the BBUV beam around 306.4 nm and Nd:YAG laser at 532 nm are focused on an air-propane premixed flame and the generated signal is spatially filtered and directed into 1 m single grating monochromator to be dispersed on an intensified CCD.