As I measured PL(photoluminescence) spectroscopy, I found that DI water in quartz cell showed a peak at about 430 nm. (quartz cell with no solution have no signal)
It is confirmed that the wavelength of the peak is not double or half value of excitation wavelength and DI water is not contaminated.
Do any one know why is that or ever observe similar phenomenon?
(Hitachi F-4500 Fluorescence Spectrophotometer
Excitation Wavelength : 375nm
EX slit : 5.0
EM slit : 10.0
PMT : 1000V)
That may be the Raman signal from the excitation source, you can check it by changing the excitation wavelength and monitoring this signal peak shift at the same time, if the peak shifts with the excitation wavelength, that can be sure the the peak comes from the Raman signal.
That may be the Raman signal from the excitation source, you can check it by changing the excitation wavelength and monitoring this signal peak shift at the same time, if the peak shifts with the excitation wavelength, that can be sure the the peak comes from the Raman signal.
Water Raman peak (397nm), when excited with 350nm, is actually used to re-calibrate the emission monochromator when required. You can check the manual of your Fluorescence Spectrophotometer. It appears, from your details, that 397 nm peak is now at 430nm (approx. 30 nm shift). If this is the case, you need to re-calibrate the monochromator to make it at 397nm. In order to find whether that is a Raman signal you can follow the method suggested by Zhang. Another way is to use polarizers. Scattered light is mostly polarized. Just use any orientation (H or V) and see if that peak disappears.
Good luck.
There is a correction required in my answer. I wrote it wrong. You should excite with 350nm and see 397nm, water raman peak. If there is any shift from this, you need to recalibrate the emission monochromator. It is not surprising, when raman scattering is involved, the peak keeps shifting with excitation wavelength. You may have 430nm peak when exciting with 375nm. And therefore you should first check calibration.
I mentioned about 30nm shift which is not true with excitation 375nm and seeing 397nm peak. It's when you excite with 350nm and see 397nm raman peak.
Dear Zhang and Kumar
I appreciated both of your answers. At this issue, I further checked if the peak would shift with the excitation wavelength. And the result was that the peak did shift. Moreover, the energy difference between excitation light and peak position is almost constant, which is the characteristic of raman signal. In addition, I also checked the peak position produced by 350nm excitation source, which is 398 nm. I thought the instrument is precise enough for my experiments. THX
It is Raman line of water. Keep changing excitation wavelength and check whrther it shifts. Then it is Raman line
This is your Raman line, as they describe above. To prove it you should try changing the pump wavelength.
To be more convincing and save you the time of changing the pump wavelength to 350nm we can do math. The energy difference between the 350nm pump and 397nm Raman line described by Kumar is 420meV. This approximately the same as the energy difference between 375nm and the emission line you observe at 430nm. No recalibration of your instrumentation is necessary. Math saves the day.
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