What are the S(x)-S(y) rotation lines?

[amarante]

Hi,

I really tried to find some explanation about this notation S(x)-S(y), but I couldn't find any! I am reading a paper about Excitation of H_2 in Photodissociation regions, and it all the time say something like:

"we find that the model can account for the first low H2 rotational line (e.g., 0-0 S(0)-S(1)) probing the bulk of the gas at moderate temperature, as well as the ro-vibrational line (e.g., 1-0 S(1)"
What are exactly the transitions 0-0 S(0)-S(1)? And the difference between them to 1-0 S(1)?

If someone could give a reference explaining this notation I would be very glad.

Thanks in advance,
Amarante

 

[SpectraCat]

Hi,

I really tried to find some explanation about this notation S(x)-S(y), but I couldn't find any! I am reading a paper about Excitation of H_2 in Photodissociation regions, and it all the time say something like:

"we find that the model can account for the first low H2 rotational line (e.g., 0-0 S(0)-S(1)) probing the bulk of the gas at moderate temperature, as well as the ro-vibrational line (e.g., 1-0 S(1)"
What are exactly the transitions 0-0 S(0)-S(1)? And the difference between them to 1-0 S(1)?

If someone could give a reference explaining this notation I would be very glad.

Thanks in advance,
Amarante

The S lines are lines for two-photon excitation processes where the change in angular momentum is +2. You may recall the R and P branches corresponding to ro-vibrational transitions with \Delta J=\pm1? Well for two photon transitions, you can have \Delta J=0,\pm2. These are called the Q, S and O branches.

Note that you can have a Q-branch in single-photon spectra as well, if the molecule possesses an internal rotation axis (e.g. symmetric top, asymmetric top, or spherical top molecules).

Note that since they are talking about H2, these transitions are probably Raman transitions. The 0-0 S(0)-S(1) is a rotational Raman transition (the 0-0 part is likely referring to vibrational quantum numbers). The other transition (0-1 S(1)) should be a ro-vibrational transition between the J=1 level in the ground vibrational state to the J=3 level in the excited vibrational state.

 

[amarante]

Thank you so much! I could only find the R and P branches.

Could you recommend a book or paper explaining the Q, S and O branches? I need it, because I am preparing a seminar and I would need a reference.

Thanks,
Amarante

 

[SpectraCat]

Thank you so much! I could only find the R and P branches.

Could you recommend a book or paper explaining the Q, S and O branches? I need it, because I am preparing a seminar and I would need a reference.

Thanks,
Amarante

I don't have a copy of Herzberg handy, but I am almost certain it is in there ... most everything of import pertaining to spectroscopy is in there. A textbook on Raman spectroscopy should also cover this.

 

[amarante]

Thank you for the help!

I am going to look for it