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Solntsev Pasha
solntsev@univ.kiev.ua

I am study spectroscopic properties of molecules and have found problem and .... few questions.

My main task is computation of UV-Vis and Luminescence properties.
Before start my real job i checked formaldehyde molecule.

UV-Vis:
1) I made geometry optimization with symmetry (C2v), DFT(PBE96/6-31G*) => get geometry of main state.
2) I made TDDFT single point energy run (using optimized coordinates) at the same basis set to get excitation energies. Ok, state #2 is state of my interest. So, now i get information about Absorption properties of my molecule(oscillation strength, energy).

Luminescence:
I need to know energy of following states

S1*
/\ \
||   S1
||   ||
||   \/
||   S0*
|| /
S0

Where:

S0 - main state
S1* - excited "unrelaxed" state
S1 - relaxed excited state
S0* - unrelaxed main state.
"==>" - emission and excitation, respectively.

So, from step 1 and 2 i got S0 and S1* states. They have same geometry but different properties(energy, symmetry ...)

3) I know, i can't use TDDFT to get geometry of S1 state. So i chose cis approximation.
3a) $CONTRL RUNTYP=optimize CITYP=cis $END
   $cis ncore=0 nstate=2 $end
ok, i got equilibrium geometry of S1 state.

4) my main problem: How can i get energy and geometry of S0* state?
Any suggestions?  

Also, how can i understand istate=-2 notation in tddft/cis groups?
I read from  DFT link:
"The state-tracking feature of the PC GAMESS/Firefly' TDDFT code can be activated by selecting negative value of istate in the $TDDFT group. It is intended for geometry optimization of the excited states in the case of root flipping.".
I don't understand how can i use this option for geometry optimization (tddft does not support gradient yet).


Best, Pavel.