MadSci Network: Chemistry

Re: What tools/equipment are used to measure luminous intensity?

Date: Fri Sep 24 11:39:20 1999
Posted By: Uncle Al Schwartz, Organic synthetic chemist
Area of science: Chemistry
ID: 938133471.Ch

It depends...  A good look would require initially knowing intensity versus 
wavelength from the near ultraviolet to the near infrared, and following 
wavelengths of interest or the whole spectrum over time.  As your system is 
emitting light, optimally you would use a fast scanning spectrofluorimeter 
(without its excitation source).  Can you borrow use of university 
equipment or secure an instrument manufacturer's cooperation?

A quick and dirty look would get by with a photodiode and some simple 
circuitry to monitor its readout.  This would only give you averaged 
readings and you would need carefully control all variables of sample 
geometry, time, concentation, mixing rate... temperature, which also effect 
the reading.  If the wavelength composition of emission shifts then you 
need a sensitivity vs wavelength calibration curve for the photodiode.

Slightly better than the worst case is to put a narrow band optical filter 
in front of your diode to get some idea of intensity vs one 
narrow wavelength band.

In any case, you need a (stirred) thermostatted sample cell.

Uncle Al!

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