Judicious placement of the boxcar time gate allows preferential measurement of the fluorescence signal this simple approach offers a relatively simple way to extract the desired signal from the elastic background. Considerable effort has been made to employ UV interferometry as an alternative to time gating. A Fourier transform of the interferogram should allow a spectral extraction of the narrow atomic mercury fluorescence line from the spectrally broader excitation light. This task proved to be formidable. A difficult, but obtainable, goal of the demonstration of UV fringes is near, and once shown, this effort will end, with a return to gating.
Work is complete on the complementary experiment, which is providing insight for the jet experiment.
An atmospheric pressure flow cell with optical access has been used to gather considerable data on PFF of mercuric bromide in argon. Limits of detection were estimated for both photomultiplier tube and CCD detectors. The PFF technique used 222 nm laser radiation to photolyze HgBr2 and excite fluorescence from the resulting Hg atoms at 253.7 nm. The PFF was collected and focused through dual interference filters, centered at 253.7 nm, into a photomultiplier tube. Extrapolated detection limits by this method below 1 ppb of HgBr2 in the absence of air were estimated.