Fellgett Advantage

An argument in favor of diode arrays is the advantage afforded by the Fellgett effect (also known as the multiplex effect or multiplex advantage). The "Fellgett advantage" is most advantageous when the measurement is otherwise difficult. Absorbance millisecond scans with milliabsorbance sensitivity are very easily and successfully achieved with the Olis RSM 1000, so any benefit of the Fellgett effect would be superfluous.

In rapid-scanning fluorescence, however, where the light level is generally low and therefore more challenging to acquire well in milliseconds, one has an argument for the Fellgett advantage. We offer an Olis ScanDisk with the Fellgett effect: a Spoke Wheel. The Spoke Wheel ScanDisk sends 100% of the light through the sample, except for the wavelength(s) behind the wavelength-marking spoke.

This Spoke Wheel ScanDisk is open across the scan aperture of the DeSa monochromator, except for a 1 mm wide spoke. Thus, only those wavelengths behind the spoke at any given instant are not available for the reading, so that the measurement enjoys the Fellgett advantage of a diode array. With all of the emission light available for detection, sensitivity is extremely high, even when collected on a millisecond time scale.

Both the narrow slit and the wide spoke wheel as intermediate slits in the Olis RSM 1000 produce high precision, high sensitivity spectral data for global data analysis and thereby best kinetic results. The Fellgett advantage is realized in the emission mode - as in tryptophan scanning over the 300-450 nm range - and is not needed in the absorbance mode, since the Olis RSM 1000 already acquires 1,000 scans per second with (sub)milliabsorbance sensitivity.

View a dynamic simulation of the ligh throughput of the RSM.

Learn more about the ScanDisk Spoke Wheel.

Learn more about microsecond kinetics with the RSM 1000.