# CCL:G: Time dependent properties

*From*: Ramon Crehuet <rcsqtc]|[iiqab.csic.es>
*Subject*: CCL:G: Time dependent properties
*Date*: Fri, 21 Dec 2007 16:36:35 +0100

Sent to CCL by: Ramon Crehuet [rcsqtc(_)iiqab.csic.es]
Dear CCLers,

`I was helping a colegue in the interpretation of an absorption
spectra.
``I used TD-DFT for the singlet states. Now she asked me to consider a
``low-lying triplet. I checked and saw that Gaussian can do triplets and
``singlets with the option 50-50. If I am not wrong, this singlet-triplet
``transitions are only allowed by the spin-orbit coupling, therefore a
``'normal' calculation will always give a null oscillator strength. Am I
``right about that? What would then be the easyiest way to proceed from
here?
` Thanks in advance,
Ramon