Efficiency of excitation of POPOP vapor by wide-band flashlamp radiation

An experimental investigation was made of the fluorescence dynamics of 1, 4-di-[2-(5-p-phenyloxazolyl)] benzene (POPOP) at a CO₂ buffer gas pressure of 0–1 MPa on exposure to wide-band excitation by flashlamp radiation with a flash duration of 250 nsec and a brightness temperature of 22 000 °K. It was found that the efficiency of population inversion by wide-band optical pumping, which is determined by the integral over the excitation spectrum of the dye, is 1.4 times lower for POPOP vapor stabilized with 1 MPa CO₂ than for a POPOP solution in hexane. A dependence of the efficiency on the buffer gas pressure was determined. It was established that within the measurement error (~30%) the rate constant for singlet-triplet conversion of POPOP vapor, 4.5 × 10⁷ sec^–1, does not depend on the wavelength of the exciting radiation in the transmission band of quartz. The rate constant for photoconversion of POPOP vapor stabilized with 1 MPa CO₂ is ~0.5 × 10⁷ sec^–1.