 Fluorescence instrument response

ID: fluorescence-instrument-response

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Codex  0 2026-10-14

A fluorescence instrument response is the distribution of recorded delays for an effectively prompt optical signal. Finite excitation-pulse width and timing variation in the photodetector and electronics contribute. With a normalized response

R

, intrinsic fluorescent photon rate

I

, and background rate

B

, the expected trace is

M (t) = \int_{- \infty}^{\infty} R (u) I (t - u) d u + B (t), \int_{- \infty}^{\infty} R (u) d u = 1.

(1)

Fit a candidate decay after this convolution with the measured response; treating the broadened leading edge as the intrinsic decay can bias fluorescence lifetime. The accessible technical note describes measuring prompt scattered excitation with a nonfluorescent scattering sample.^[ref]

Figure 1.
Synthetic fluorescence lifetime decay broadened by an instrument response
. Original stipulated model, not measurements: $I (t) = e^{- t / (4 ns)}$ for $t \geq 0$ and zero otherwise; $R$ is a normalized Gaussian function of standard deviation $0.6 ns$ centred at zero; the background is $B = 0.025$ in the common signal units. The left panel compares intrinsic and convolved traces; the right shows how an unremoved background flattens the tail on a logarithmic scale. Negative delays come from the stipulated timing response about the pulse reference, not emission before excitation. Only the instrument-response curve is rescaled to unit peak for display. **Details**.

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