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How to understand the negative twophoton transition strength 
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#1
May1814, 09:18 PM

P: 14

Dear all,
I have calculated the rotationally averaged twophoton transition strength (DeltaTPA) using the CCSD response approach. Degenerate TPAs of ten excited states have been calculated. For most of the excited states considered, I got the positive DeltaTPAs, while for some excited states, I got the negative DeltaTPAs. The negative DeltaTPA will lead to the negative TPA cross section, then to the negative TPA absorption coefficience (beta). My question is: whether the negative beta can be related to the saturable absorption process. Any references and comments are appreciated. Best regards. Lan 


#2
Jun1114, 04:18 PM

Admin
P: 9,575

I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?



#3
Jun1114, 07:04 PM

P: 14

Thanks for your attention. I also ask for help on the forum of DALTON program which implements the CCSD response calculation for TPA. Unfortunately, I haven't gotten the response. Bests Lan 


#4
Jun1214, 03:39 AM

P: 231

How to understand the negative twophoton transition strength
I'm not familiar with with the specific technique you have used but I can give a more general comment.
Generally, when one is talking about negative absorption coefficients, what is meant is that you have a gain situation, i.e. stimulated emission, most often coming from some form of inverted population. 


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