Frequency Domain (FD) fluorimetry, capitalizes on the frequency response function of a fluorophore and offers independence from light scatter and excitation/emission intensity variations in order to extract the sample's fluorescent lifetime. Mercury vapor lamps, a common source of industrial facility lighting, emit radiation that overlaps the UV/blue absorption spectrum of many fluorophores and may be used as an efficient and portable excitation source. The AC power modulation of mercury vapor lamps modulates the lamp's intensity at 120 Hz (in the United States) and higher harmonics. The fluorescent lifetimes for 3 different materials (willemite, uranium doped glass and U3O8) are measured with conventional techniques and compared with the FD technique using the power harmonics from a mercury vapor lamp. The mercury lamp measurements agree to within 25% of the conventional methods.
Phase Fluorimetry, or Frequency Domain (FD) Fluorimetry, capitalizes on the phase delay from excitation modulation of fluorescent media and offers independence from light scatter and excitation/emission intensity variations in order to extract the sample's fluorescent lifetime. Samples which fluoresce in the UV are commonly excited with UV laser sources, which are not necessarily high power, portable devices. Mercury vapor lamps, a common source of industrial facility lighting, emit wavelengths (365 nm, 405 nm, and 436 nm) that overlap the UV/blue spectrum and may be used as an efficient and portable excitation source. Mercury vapor lamps show strong peak intensities at 120 Hz and higher harmonics, due to the modulation of facility power at 60 Hz in the United States. For this research effort, single exponential decay will be assumed and lifetime calculation will be performed by least squares analysis with corrections made for lamp intensity variations at the harmonics of facility power.
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