how to calculate stokes shift of a molecule which is having absorbance at 307 nm and emission at 469 nm?
From https://en.wikipedia.org/wiki/Stokes_shift
"Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and emission spectra (fluorescence and Raman being two examples) of the same electronic transition. It is named after Irish physicist George G. Stokes.[
So, your Stokes Shift is 469 nm - 307 nm = 162 nm
I think the difference here is the perspective of the average biologist vs. those with a more physics/chemistry oriented view of things. A very reputable microscopy education and resource website describes Stoke's shift as per John (see the link). This is aimed at biologists and is probably way too oversimplified for the die-hard photophysics people...
http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorescenceintro.html
Thanks for the clarification Peter Kapusta! Perhaps you could edit the wikipedia page [1], citing Gonzalo Angulo, et al [2], saving me and others from repeating this common error?
If I understand correctly:
- Convert nm, wavelenghth to cm-1, absolute wavenumber before subtraction: the unit conversion really matters!
[1] https://en.wikipedia.org/wiki/Stokes_shift (The science wiki pages are usually so good, compared to others)
[2] Recalling the appropriate representation of electronic spectra,Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Volume 65, Issues 3–4, November 2006, Pages 727–731 (See Attached)
@John
Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and emission spectra
This is wrong: it should be
the difference in energy between the first band in absorption versus the firt band in the emission spectrum
This is often NOT the maximum in the respective spectra
Questioner
1. Provide the spectra
or
2. What is the wavelength or wavenumber (energy) of the first band in absorption and the first band in emission
Actually looking at the figures the questioner this is a (too) huge energy difference for a Stokes shift caused by a solvent effect; maybe the absorption is to a higher excited state?!
Questioner what compound is it?
The Stokes shift is the difference between the absorption and emission maxima. In this case, the value is 162 nm.
(469 - 307 = 162)
No it is not it is the difference in the energy of the first "peak" in the absorption and emission spectra
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