Absolute quantum efficiencies

Abstract

Recent deve lop ments in severa l areas of chem istry, laser technology, photod etector in strum e ntation, a nd calorim etry are su rveyed , and thei r probable impact on th e measurement of quantum yi elds is assessed. C he mical developments incl ude: (a) synthesis a nd design of ne w luminesce nt mol ecul es that cou ld possi bl y serve as standards, (b) a pplication of improved se pa ration techniques to provide sam pl es of extreme purity, and (c) advances in photoch",m istry that port e nd th e developm e nt of widera nge c he mical actinomete rs. Th e potential use of lase rs in qu antum-yield meas ure ments and th eir adva ntages ove r co nve ntional so urces for ap plication in both opti cal and calorim etric te c hniques are pointed out. New methods of quantum-yield meas urements, based o n the novel c harac te ristics of lase r pump sou rces, a re suggested, in cl udin g th e feasibility of meas urin g yields unde r time-reso lve d co nditions and of employing internal standards. The poss ible liftin g of wavelength restri ctions on both laser so urces a nd de tector devices a nd the impli cation s of these de ve lopments for exte ndin g the spec tral range of quantum-yield measurements are discussed. The c urre nt status of calorim e try for dete rminin g yield s is surveyed , and th e impact of rece nt te c hnology on the feas ibility of deve loping ca lorim e tric method s com pe titive with opti cal me thods is assessed.Key words : Calorime try in quantum yields; laser, use in quantum yie lds; photodetectors in quantum yields; quantum effi cienc ies_

Fluorescence Quantum Yields and Their Relation to Lifetimes of Rhodamine 6G and Fluorescein in Nine Solvents: Improved Absolute Standards for Quantum Yields¶

“…As an alternative to measuring quantum yields, k r might be calculated using the Strickler-Berg relation (2). There are, however, reasons (3) to doubt that adequate precision could be obtained. At the time of that report, we were equally dubious about measuring accurately because of wellknown difficulties (3) in measuring quantum yields.…”

Fluorescence Quantum Yields and Their Relation to Lifetimes of Rhodamine 6G and Fluorescein in Nine Solvents: Improved Absolute Standards for Quantum Yields¶

“…As an alternative to measuring quantum yields, k r might be calculated using the Strickler–Berg relation (2). There are, however, reasons (3) to doubt that adequate precision could be obtained. At the time of that report, we were equally dubious about measuring φ accurately because of well‐known difficulties (3) in measuring quantum yields.…”

“…There are, however, reasons (3) to doubt that adequate precision could be obtained. At the time of that report, we were equally dubious about measuring φ accurately because of well‐known difficulties (3) in measuring quantum yields. It is a challenge to measure a relative yield to 5% precision, and the standards to which relative yields are referred are themselves uncertain by 5% or more.…”

The calorimetric detection of excited states

“…1 In the absence of photochemistry, the fluorescence energy yield is the complement of Y h , and the quantum yield of fluorescence Φ f is related to it by the formula where and are the average frequencies of absorbed and emitted photons respectively. Calorimetric quantum yields determined in this manner [ 1 , 2 , 3 ] are among the most precise and accurate reported in the literature, and in addition provide a valuable independent technique for verifying the many assumptions that go into the derivation of quantum yields from photometric measurements [ 4 , 5 ]. Despite these advantages, very few quantum yields have been measured calorimetrically.…”