Fluorescence spectra, PDAs

Photodiode Array Versus Photomultiplier Detection. The advantages of photodiode array detection, PDA, as compared to photomultiplier tube, pmt, detection for emission spectroscopy are well known (19). These advantages are especially important for the specific examples we discuss here, namely, upconverting emission spectroscopy. This is dramatically demonstrated in Figure 7 where we compare single channel pmt versus multichannel PDA detection of a small portion of the upconverted fluorescence spectrum of coumarin 520 in ethanol solvent at room temperature. 

The fluorescence spectrum of this molecule is broad and structureless in the wavelength region of Figure 7. With PDA optical multichannel detection we observe, as expected, no signal at negative delay time with respect to the arrival time of the 355 nm pulse at the sample, and at 200 psec after the pulse arrives, the broad structureless spectrum of coumarin 520 is observed. The experimental parameters were as follows ... 

Figure 4. Fluorescence emission spectrum of 5 mol% PDA in monolayer LB PMMA film transferred at 7 dyn/cm. The excitation wavelength is 343 nm.

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