ACOUSTIC-WAVE DOSIMETRY BASED ON DIAZOTIZED LUMINOL SOLUTIONS

High-power pulsed microwave fluences interact with aqueous solutions i n a complex way. The incident energy partitions into direct heating (g enerally on the side facing the source) and an acoustic wave transient (the so-called microwave acoustic effect) which may dissipate thermal energy differently based on absorber geometry and acoustic wave inter ference. Iu a search for chemiluminescent (imaging) dosimeters suitabl e for distinguishing direct heating and acoustic wave phenomena, we fo und that dilute solutions of diazotized luminol produce a reliable 200 -fold luminescence increase above the quiescent condition when 115 mi of the solution is subjected to 62 W of 20-kHz acoustic energy. The co ntrast ratio (irradiated to quiescent) is markedly diminished and irre producibility is introduced if carbon dioxide is not thoroughly exclud ed from the dosimeter solution by bubbling with nitrogen gas before us e. Dissolved carbon dioxide acts mainly to increase quiescent thermoch emiluminescence. The ratio is largest if the dosimeter solution is chi lled to 0 degrees C. The contrast ratio is pH dependent and maximum be tween pH 7 and 7.5, and sonochemiluminescence generated in this manner fades with a time constant of about 0.5 s when the irradiation is sto pped. The light output from this dosimeter is well above the sonolumin escence produced in pure water under the same irradiation conditions. (C) 1998 Academic Press.