Integrating-sphere fluorescence cells: instrumental errors in fluorescence lifetimes and intensities

An integrating-sphere fluorescence cell is described for measurement of intensities, yields, and lifetimes of long-lived gas phase molecules under collision-free conditions. The cell has high light-gathering efficiency and provides uniform sampling and a well-defined source for imaging onto the detection system. The signal gain compared to a conventional fluorescence cell of similar dimensions may be as great as 100-fold. Expressions are developed for measurement errors as a function of cell radius. For equal errors the integrating sphere radius must be 2-3 times that of a conventional cell.