Fluorimeters steady state

The spectroscopy described thus far is based on the measurement of the intensity of fluorescence produced under steady-state conditions of excitation. Steady-state fluorimetry is derived from the excitation of the sample with a continuous beam of exciting radiation. The lamps and the power supplies used in conventional fluorimeters are sources of continuous radiation. After a short period of initial excitation of the sample, a steady state is established in which the rate of excitation of the analyte is equal to the sum of the rates of all processed, deactivating the lowest excited singlet state including fluorescence. When fhe sfeady state... 

The simplest way to measure energy transfer is to measure the decrease in fluorescence of the donor in the presence and absence of acceptor. The fractional decrease in the donor fluorescence with the acceptor present is equal to the efficiency of energy transfer [see Eq. (1)]. The only instrumentation necessary is a steady-state fluorimeter. Besides simplicity, the steady-state measurement has the advantage that even a relatively small amount of energy transfer can be measured. If care is taken in measuring concentrations and in the spectroscopy, a 5% decrease in fluorescence is measurable this corresponds to a distance of 1.6 / o- One caution is that the optical density (OD) of the sample must be kept sufficiently low that no appreciable absorption of the donor fluorescence takes place less than... 

Steady state absorption and fluorescence measurements were made using a Perkin-Elmer 554 spectrophotometer and a Perkin-Elmer MPF-4 fluorimeter. Fluorescence lifetimes were measured using time-correlated single photon counting [5,7]. Details of the analysis of the decays can be found in [7]. 

Gas exchange of attached leaves of Phaseolus vulgavis, steady state chlorophyll fluorescence and 820 nm absorbance changes (monitoring the redox-state of P700) were measured simultaneously (using a pulse-modulated PAM fluorimeter/photometer from Walz), basically as described in [4,5f6]. To keep the rate of photorespiration low,... 

ISA s (Spex s) Fluorolog Tau-3 lifetime system and Spectronic Instruments SLM-AMINCO 48000 DSCF spectrofluorimeter both use xenon flash lamp excitation (t5 ically 150-450 W) and have modulation frequencies of up to 310 MHz. (Most systems can also be operated as steady-state fluorimeters). SLM also manufactures a multi-harmonic s3rstem based on a pulse- modulated continuous wave light source. 

Fluorescence spectrometers are a very well established class of commercial scientific instrument, and need not be further described here, as they are well described elsewhere. For example, a schematic diagram of the basic components of a steady-state fluorimeter is given in Ref. [45], and a review of fluorescence instrumentation is also given in Ref. [46]. 

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