OpenRaman on homonuclear diatomic gas molecules

[NaHBrO]

Hello Forum,

the affordability of the OpenRaman build is of interest to our university labclasses because for future teachers it can serve as inspiration for what they might one day do with their classes. We have therefore ordered the needed parts for a starter version and are preparing to integrate some experiments with it into our curriculum. Furthermore we believe that, because we teach physics, using it on diatomic molecules might be of special interest, due to the relative simplicity of solving the two body problem as opposed to more complex structures. The obvious choise of samples would be diatomic gases like nitrogen, oxygen and maybe hydrogen. But ofcourse gases have a much lower density than liquids and I have thus far only seen examples where OpenRaman was used on liquids. Has anyone ever tried the build on gases? If yes what were your experiences with it?

Thanks for answering in advance.

[andy]

That might be tough based on my understanding,

In Raman spectroscopy [1] McCreery notes that the how much raman signal you get back per molecule seems to be less in gas phase vs liquid by about a third (page 25). Given it's already .1% as dense you are looking at .03% concentration or 300ppm. I think that's in the range of the "performance edition" (in other words using a stronger laser) though you are looking at some long exposure times and potentially not the cleanest spectra. I'd be interested to hear if you can get it working.

Another factor is according to the same book, same page, those gasses might not have that strong of a raman signal. The absolute raman cross section for one of their peaks is in the range .4-.6 whereas an example cross section peak for benzene gas is 7.

[1] McCreery R. L. (2000). Raman spectroscopy for chemical analysis. John Wiley & Sons.

[NaHBrO]

Thanks for your answer. I will have to build it in the frist place to get a better idea of how sensitive the spectrometer is. Maybe we will have to upgrade to the performance edition after all. Another idea that I had was to maybe use some diatomic molecules that are liquid at room temperature (we do have access to liquid nitrogen but that might damage the cuvette). I found that Bromine might give us what we wanted since its natural state a room temperature is liquid and it seems to form Br2 molecules. If we managed to heat up the cuvette to an appropriate temperature maybe iodine might also be an option since then it would have I2 molecules (although 114°C might still be challenging to get for it). I am not a chemist and therefore I am not completly sure if there are any things that I missed. Maybe there are intermolecular interactions that might overshadow the transitions that we wish to capture.