title: Detector nonlinearity in frequency-domain fluorometry.
abstract: Frequency-domain fluorometry relies on the measurement of the phase and amplitudes of the Fourier components of the time-dependent fluorescence signal. Experimental results that show that a conventional photomultiplier is subject to intensity-dependent phase shifts are presented. The measurements indicate that this is a problem well below the maximum linear current of the photomultiplier response. These results have important implications in frequency-domain fluorescence anisotropy experiments, in which the parallel and the perpendicular components of the emission intensity are inherently different from one another: a phase shift can be introduced by the photomultiplier.
authors.forename: M J
authors.initials: MJ
authors.lastname: Wirth
authors.forename: J D
authors.initials: JD
authors.lastname: Burbage
authors.forename: S L
authors.initials: SL
authors.lastname: Zulli