## Transition moments with CCQR2R

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tatami1
Posts: 4
Joined: 20 Jan 2020, 17:53
First name(s): Giuseppe
Last name(s): Chen
Affiliation: La Sapienza
Country: Italy

### Transition moments with CCQR2R

Hi! I've calculated the transition moments between excited states using CCSD with the command CCQR2R, but I'm having trouble with the interpretation of the output:

S{XDIPLEN ,XDIPLEN }( 0.170457 -> 0.189089) = 0.01748457 ( 0.13222924)
S{XDIPLEN ,XDIPLEN }( 0.170457 -> 0.191983) = 0.56162239 ( 0.74941470)
S{XDIPLEN ,XDIPLEN }( 0.189089 -> 0.191983) = 0.00096864 ( 0.03112293)
S{XDIPLEN ,XDIPLEN }( 0.170457 -> 0.197138) = 0.08929238 ( 0.29881831)
S{XDIPLEN ,XDIPLEN }( 0.189089 -> 0.197138) = 0.00957655 ( 0.09785984)
S{XDIPLEN ,XDIPLEN }( 0.191983 -> 0.197138) = 0.09321932 ( 0.30531840)

I'm not sure if the transition moments are the values between parentheses or those outside of them. Also, is the the sign the correct one or do I have to multiply by -1?
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magnus
Posts: 524
Joined: 27 Jun 2013, 16:32
First name(s): Jógvan Magnus
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Affiliation: Aarhus University
Country: Denmark

### Re: Transition moments with CCQR2R

From https://doi.org/10.1063/1.475671 it looks like the first value is the transition strength element defined as S_XY^if = 1/2*(<i|X|f><f|Y|i> + <i|Y|f><f|X|i>) and from the code I can see that the second value in parentheses is the square root of S_XY^if if it is positive and minus the square root of -S_XY^if if it is negative.

tatami1
Posts: 4
Joined: 20 Jan 2020, 17:53
First name(s): Giuseppe
Last name(s): Chen
Affiliation: La Sapienza
Country: Italy