G. R. Haugen

Optimization of data-acquistion rates in time-correlated single-photon fluorimetry

Four different operating configurations of a time-to-amplitude converter were examined for performance in the time-correlated single-photon fluorimetric experiment. Parameters considered were the intensity/count linearity, maximum data rate, and decay distortion. The inverted configuration with an interactive source was optimum. This arrangement combined total linearity with a 37-kHz conversion rate and did not distort the fluorescence decay. In addition, the pulse-height analyzer could severely limit the overall system data rate and could destroy the TAC intensity/count linearity.

Correction of quenching errors in analytical fluorimetry through use of time resolution

Abstract Varying concentrations of quenching agents can cause serious errors in analytical fluorimetry. The origin of these errors is an unexpected change in the quantum efficiency for the observed luminescence. It is known that quantum efficiency can be expressed as the ratio of an observed luminescence decay time to the decay time which would be observed in the absence of quenchers. Because this latter quantity is a constant for any particular fluorophore, quantum efficiency variations can be compensated through measurement of the decay time. For such measurements, the time-correlated single photon technique was employed and measured luminescence values were taken both from averaged photon count rates and from integrated fluorescence decay plots. Division of these values by measured luminescence lifetimes produced values which were independent of quencher concentration. Systems studied were quinine bisulfate quenched with chloride ion and 1-pyrenebutyric acid quenched by iodide.

Time-resolved laser-induced fluorescence with high-performance liquid chromatography for analysis of polycyclic aromatic hydrocarbon mixtures

Abstract Time-resolved fluorescence is used to enhance the selectivity for polycyclic aromatic hydrocarbon mixtures by high-performance liquid chromatography. A pulsed laser is used as the excitation source. Only fluorophores with long fluorescence lifetimes (e.g. fluoranthene) are monitored if the delay between excitation and detection is sufficiently long. Limits of detection are of the order of 1–10 pg (5–50 fmol). The advantages are illustrated with a sample from the condensed steam distillate following a coal gasification experiment.

New method for the determination of luminescence lifetimes by using the beat noise of a cw laser as a multifrequency‐modulated source

The excitation of a fluorophore by rapidly varying fluctuations in a free‐running argon‐ion laser is shown to produce variations in measured fluorescence. The power spectrum of the fluctuations can yield lifetime information on luminescence and the experimental apparatus described exploits this phenomenon. Methods of improving the measurements are also considered.

Time-Resolved Fluorimetry Via a New Cross-Correlation Method,

A new instrument for the measurement of short fluorescence lifetimes is discussed and characterized. The instrument is basically an implementation of the cross-correlation between the excitation source and the induced fluorescence response. Such an approach, with a mode-locked argon-ion laser as the source, is shown to be capable of measuring lifetimes as short as 80 psec with a precision of 10 psec.

Wide-bandwidth analog correlator and its application to mode-locked laser measurements.

A new instrument for the analog determination of correlation functions of wide-bandwidth signals is described and characterized. The instrument is comprised of microwave electronic components; a double-balanced mixer performs the multiplication operation involved in the correlation process, whereas a constant-impedance line stretcher introduces the variable delay. Measurements indicate that the correlator has a bandwidth of approximately 3 GHz. It is shown that this inexpensive and simple device can be used as a diagnostic tool for mode-locked argon-ion lasers when used in conjunction with a fast photodiode detector.