Specifications

Fluorescence Correlation 27
The curves to be displayed in the display windows for the accumulated counts, FCS curves,
and MCS traces are defined under ‘Trace Parameters’. Each display window has its own trace
parameters. To open the trace parameters, click on ‘Display’, ‘Trace Parameters’. A click into
one of the curve windows selects the right trace parameter set. Alternatively, you can click in
the desired curve panel with the right mouse key, and select ‘Trace Parameters’. Examples of
the trace parameters are shown in Fig. 38. The trace parameters for the ‘Counts’ window acti-
vate the display of the accumulated counts for two detectors, connected to channel 4 and
channel 6. The trace parameters of the FCS window are set to calculate and display an FCS
curve for channel 4, and a fit to the data in channel 4. The trace parameters for the MCS win-
dow define traces for channel 4 and channel 6.
Fig. 38: Left to right: Trace parameters for Counts window, FCS window, and MCS window
A result of an FCS measurement with these parameters is shown in Fig. 39. The photons were
acquired by two detectors, at an average total count rate of 260,000 photons per seconds. The
total acquisition time was 46 seconds. The figure shows the accumulated counts of both detec-
tors, the FCS (autocorrelation) of the detector connected to channel 4, and MCS traces for
both detectors.
Fig. 39: Result of an FCS measurement
Cross-Correlation between different detector channels is obtained by simply defining the
channels to be correlated in the trace parameters, see Fig. 40, left. The parameters shown cor-
relate DPC channel 4 against channel 6, and run a fit on the calculated cross-FCS curve. The
result is shown in Fig. 40, right. The data points are shown pink, the fit with a single diffusion
time and a triplet time is shown black. The result of the fit is displayed by clicking on the
‘Trace Statistics’ button. They are shown as an insert in Fig. 40, right.