A PHASE SHIFT METHOD OF DETERMINING MILLICROSECOND FLUORESCENT LIFETIMES OF ORGANIC SUBSTANCES IN AERATED SOLUTIONS.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
Pagination or Media Count:
An apparatus is presented to measure fluorescent lifetimes of organic substances in aerated solutions. The apparatus employs the phase shift method of measurement, which is useful for determining lifetimes in the range of 10 to the -7th to 10 to the -9th seconds. When a fluorescent substance is irradiated by light modulated bat frequency omega, the fluorescence is modulated at the same frequency but phase-shifted by an angle phi. This angle is measured by the electrical system of the apparatus, and omega is known the lifetime upsilon is then calcu..ated with the phase shift formula tan phi omegaupsilon. The phase shift apparatus is described with respect to function, performance, and error sources, and an experimental procedure is recommended for use with the device. The fluorescent lifetime of perylene was measured to evaluate the system performance and found to be 5.1 0.5 x 10 to the -9th seconds. This value was in close agreement with that found by Ware for the same substance, using the same method of measurement. Author