METHOD FOR THE DETERMINATION OF ABSORPTION CROSS SECTIONS OF FLUORESCENT SOLUTES

点击翻译按钮获取中文摘要

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have devised a method for the determination of absorption cross sections which is independent of the concentration of solute. Our method makes use of the photon counting histogram (PCH) analysis of fluorescence fluctuation spectroscopy together with a fluorophore that can be used as a calibration standard. We demonstrate the principles of the method and its application to the measurement of two-photon cross sections of organic fluorophores at nanomolar concentrations; showing that we obtain reasonable numbers when comparing with literature values. Our method is particularly useful in cases where small amounts of sample are necessary (femtomoles and possibly less) and where the absorption cross section cannot be determined by other methods.