I am using a laser source that is wider than typical laser source for Raman spectroscopy. This mean that the full width at half maximum (FWHM) of the laser is about 5-10 nm, compared to the normal 1-3 nm.
Hypothetically, if my laser source peaks at 785 nm and has a FWHM of 10nm, this means:
- Assuming that it is 10,000 units at the peak (785 nm)
- Then I could expect 5,000 units per second at around 780 nm and 790 nm
- The intensity of the wavelengths of 780 to 785 and 790 to 785 follows a non-linear function that I can probably characterize.
If I look at a particular wavenumber in my result:
Can I express it as the sum of overlapping Raman spectras from different wavelengths?
This implies: intensity2000 = SUMMATION( ... a780 * intensity780 + a781 * intensity781 + ....), where a780 = 0.5 and a790 = 0.5, etc
I am interested to know whether there are research done in this area that could enable me to use a wider, but much cheaper, laser source.
You could do all if that, but you could never regain the ability to separate peaks (resolution) that you would have had with a narrow laser source.. Also your peaks would be spread in energy just as much as the laser meaning they would be less intense at the peak and wider which makes them closer to the noise level by some amount.
Keep in mind you may have extremely nonlinear effects (resonance) which will not allow you to use simple deconvolution functions. You can use such setup as long as you don’t need to compare with conventional instruments, but you may have a hard time convincing colleagues and publishers that you used appropriate method.
1. If your NIR laser has some 10 nm FWHM, its spectral FWHM is approx. 16 cm-1.
2. A typical FWHM for a band of an organic compound is on the order of 10 cm-1, and you might have trouble if your spectral resolution will be >16 cm-1
3. Usually, a manufacturer of a laser pointer claim that its FWHM is about 1-2 nm corresponding to ~3 cm-1, i.e., approx. x5 less than your laser.
4. However, if such "a cheap" source spoils the resolution (on a well-defined model compound) from (the instrumental) ~4 cm-1 to (the obtained) ~8 cm-1, its FWHM seems to be rather ~7 cm-1, i.e., approx. 4 nm, I would guess.
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