Principles of Fluorescence Spectroscopy. Chemistry Department XMU. Chapter Seven. Measurement of Fluorescence Lifetime & Time-domain Fluorescence & Frequency-domain Fluorescence. Content. 7.1 introduction 7.2 pulse lifetime measurement
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Phase angle ()
Demodulation factor (m)
=2f an important factor
For small lifetime, set large modulation frequency
For large lifetime, set small modulation frequency
Choosing modulation frequency, let
m = 0.3 ~ 0.7, = 30 ~ 70º
For commercial frequency-domain instrument, changing , measuring miand i, calculate average lifetime
t7.4 Measurement of Time-resolved Decays of Fluorescence
Pulse lifetime measurement
Enough shorter compare to decay of fluorescence
Enough for accurate measurement
tAnalysis of time-resolved decays of fluorescence intensity
In principle, for single exponential decay
In practice, in consideration of the pulse width of lamp and multi-exponential decay
Intensity profile of light, L(t)
Intensity decay of fluorescence, F(t)
Measured intensity decay, R(t)
In practicing measurement
At ti, a large number of pulses with equal width ti, each induce an impulse response in the sample
t - ti, emission delay compare to excitation
Total intensity decay,
The purpose is to get F(t)
Commercial software available
Let the number of components to be n,
Give initial values to i and i, and calculate, get
L(t), was measured
The i and ivalues are varied until the best fit is observed.
In this expression the sum extends over the number (n) of channels or data points used for a particular analysis.
A minimum value of 2indicates the best fit.