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Techniques for Collectors473nm Laser for Raman spectroscopy

8th Mar 2017 20:18 UTCJoy Desor Expert

Has anyone experience with the 473nm laser in raman spectroscopy of minerals? I wonder if this laser can be used.

Thanks!

9th Mar 2017 08:30 UTCJoel Dyer

Hi Joy,

Did you get any response from anybody via email or other means? I see that several time-resolved experiments have used also this wavelength, so why not? I assume that the laser is naturally stablised and of SLM type?

I would imagine that the wavelength might produce somewhat less background fluorescence compared to 532nm?

Wouldn't it be great to have a tunable laser that could produce many, many wavelengths... But such a setup must be horribly expensive, what with all the different edge filters needed, too...

Cheers,

9th Mar 2017 12:52 UTCJoy Desor Expert

Thank you Joel,

no no information yet, I have talked with a technician. He said I will be okay for this kind of work.

Hmm I will couple another 532nm laser into the system then.

Cheers

9th Mar 2017 16:57 UTCStefan Oertel

Of course it would work with 473 nm though not much to no reference spectra will be available. Besides of getting a steep filter, the shorter wavelength requires either a higher resolution of the spectrometer or will result in a loss of resolution if the same is used.

A range of 1600 cm-1 corresponds to 49 nm @ 532 nm, but only to 39 nm @ 473 nm, so with the same spectrometer you would loose 20% resolution, but get a wider range for compensation.

Since the energy is higher with shorter wavelengths, I would expect more fluorescence, not less with 473 nm im comparison with 532 nm.

@Joel: you asked once how to avoid fluorescence. Besides using long laser wavelengths, you can also use very short ones. 266 nm requires only a range of 12 nm for 1600 cm-1, the spectrometer only needs to cover 266-278nm which is way below any fluorescence response. You could just cut the fluorescence off with a shortpass filter.

Cheers,

Stefan

10th Mar 2017 04:32 UTCJoel Dyer

HI Stefan, thanks for the heads-up. Must indeed have been thinking of UV or near-UV excitation when thinking of Raman fluorescence. I guess 419 nm would be the more often used wavelength in the 400-range?

Optics that pass through low wavelengths would mean a very epensive setup, including special microsope objectives (ouch!!) Always pros and cons ;-) . BTW, does anyone have laying around an extra UV-passing microscope objective they're willing to sell fairly cheaply..?

If you have loads of money, no problem. Really good / versatile systems seem to cost 250.000 - 350.000€, what I last saw in official price lists...

Good luck with the experiments, Joy! A lot of hard work, repetition and patience it needs, eh?

Cheers,

27th Mar 2017 06:30 UTCBob Rock

There will likely be too much background fluorescence for Raman with lasers below 532nm.

Cheers, Bob

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