Hardware Used:
USB2000-FLG
EG&G pulsed xenon light source
CUV-ALL-UV
600 micron optical fibers

Acquisition Parameters:
Integration Time (msec): 10
Spectra Averaged: 100
Boxcar Smoothing: 20

Measurement Mode:
Gated Fluorescence

Experimental Conditions:
The sample used was Bacillus globigii spores in terbium reagent. Data acquisition delayed from 5 to 500 usec after the lamp was triggered.

Results:
The effect of gating on the spectral shape is shown in the figures below. As the delay between lamp trigger and data acquisition is increased, the terbium/DPA photoluminescence becomes more distinct. Shorter lived background fluorescence and lamp pulse are not observed. Longer delay times (above 50 usec) lead to a decrease in sensitivity as a portion of the terbium/DPA photoluminescence is missed at long delay times.

Conclusions:
The optimal delay for these samples is 40 microseconds. A 40 microsecond delay between the lamp trigger and data acquisition minimizes the contribution of the xenon source (and fluorescence due to other fluorophores) to the photoluminescence spectrum while maximizing the photoluminescence signal.

Images: