ABII Excitation Light Source. The ABII spectrometer (figure 2E) was selected to provide well-constrained, high-resolution fluorescence spectra. To understand how its excitation compared to that of other sources, different excitation wavelengths of the ABII CW Xenon source were examined (the instrument can produce excitation of 200–950 nm). As shown in figures 4H and 4I, when the instrument was set to 365 nm excitation with 4 nm bandpass, the resultant emission showed a narrow peak at 366 nm with an FWHM of 5 nm. With a 16 nm bandpass parameter (which most closely resembled the output of a GIA LW-UV lamp), a peak was observed at 367 nm with an FWHM of 15 nm. To precisely characterize the fluorescence from a given excitation wavelength, we chose the smallest available bandpass setting (4 nm), and thus the narrowest excitation emission, for the 3D-fluorescence spectra collection.