http://confocal-microscopy-list.275.s1.nabble.com/weird-emission-spectral-peak-of-a-blank-buffer-tp7579220p7579223.html
Raman is usually pretty weak. How long are you acquiring? If this is over
a (relatively) long acquisition then yes, it could be Raman. If you look
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> Yuansheng,
> The lower wavelength small peak is the water Raman signal. The water
> Raman shift is 3382 cm-1 and the wavelength depends on the excitation
> wavelength. For your 350 excitation spectra, the Raman peak would occur at
> 397 nm. For the others you can calculate the shift using this equation:
> Raman shift (cm-1) = ((1/excitation wavelength(nm)) -(1/Raman peak (nm)))
> *10^7.
>
> The peak at twice the excitation wavelength is the second order
> diffraction peak of your excitation line. To get rid of this you will need
> to purchase a filter to remove this light from entering the emission
> monochromator. You can purchase order suppressing filters or long pass
> filters to accomplish this (you will need to talk to your fluorimeter
> manufacturer to see how this filter can be added to your system). The
> other option is to choose dyes with emission peaks that are less than
> 2*excitation wavelength.
> Best,
> Brooke Beam
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Brooke Beam, Ph.D.
> W.M. Keck Center for Surface and Interface Imaging
> University of Arizona Chemistry & Biochemistry
> 1306 E. University Blvd.
> Tucson, AZ 85721
> website: www.chem.arizona.edu/rss/keck/keck.html
> email:
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> Fax: (520)621-8407
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>
> -----Original Message-----
> From: Confocal Microscopy List [mailto:
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> On Behalf Of yuansheng sun
> Sent: Wednesday, October 24, 2012 10:27 AM
> To:
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> Subject: weird emission spectral peak of a blank buffer
>
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> Dear Listers,
>
> Recently, we got two weird peaks in the emission spectrum of our blank
> buffer (1-molar Tris at pH 7.3), measured on a spectrofluometer. The Tris
> buffer is what we use to make our dye solutions to be measured on the
> spectrofluometer. It is always freshly prepared. One small peak of the
> blank buffer shows at about 20 nm plus the excitaion wavlength and the
> other huge peak appears at about twice of the excitation wavelength. We
> found this with the emission spectrum measurements using 5 different
> excitation wavelengths - 250 nm, 280 nm, 285 nm 300 nm, and 350 nm. We
> also observed the similar things with DI water. Any explanation and
> suggestion would be appreciated. Thanks a lot in advance.
>
> Yuansheng Sun
>