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Re^5: How to check for acceptance of Kasha's rule from TDDFT data...?

Pavlo Solntsev
pavlo.solntsev@gmail.com


To be honest, i have no idea what you are trying to ask. What do you call de-excitation?

I really recommend you to play with small molecule first to understand how it works.
Do a search on this forum. People already discussed a calculation of luminescence.

-Pavlo.





On Thu Sep 25 '14 2:18pm, Siddheshwar Chopra wrote
--------------------------------------------------
>Dear Pavlo,

>Please have a look at the energies for 3 excited states from absorption and emission runs:
>EMISSION CALCULATION:: ISTATE=1, NSTATE=3

> EXCITED STATE 1 ENERGY= -1355.7217994424 S = 0.0 SPACE SYM = A

> EXCITED STATE 2 ENERGY= -1355.6780193460 S = 0.0 SPACE SYM = A

> EXCITED STATE 3 ENERGY= -1355.6756729663 S = 0.0 SPACE SYM = A
>
>
>
>UV CALCULATION:::: ISTATE=1, NSTATE=3

> EXCITED STATE 1 ENERGY= -1355.7080939866 S = 0.0 SPACE SYM = A

> EXCITED STATE 2 ENERGY= -1355.6840777343 S = 0.0 SPACE SYM = A

> EXCITED STATE 3 ENERGY= -1355.6782292662 S = 0.0 SPACE SYM = A

>
> IN ALL THE TRANSITIONS... EXCITED STATE 1 HAS THE LOWEST ENERGY...BE IT ABSORPTION OR EMISSION...So for emission, if the initial state is S1,
>then what are these excited states? Ideally speaking in this run, S1 is the ground state. The excited state 1 has the lowest energy (-1355.7217994424). Then it should be the lowest vibrational level of S0.
>Please help me in this analysis.

>Kind Regards,

>On Thu Sep 25 '14 6:47am, Siddheshwar Chopra wrote
>--------------------------------------------------
>>Dear Pavlo,
>>That is some real relief... Actually the same under study is a doped one. Sir please read my last message and answer them. The picture of Emission process is unclear to me, with regard to the firefly calculations. The ISSTATE=1 is ENSURING that we are finding a transitions from S1 only..Is it correct?
>>So now SPECIFICALLY about the emission calculations::: What are these EXCITED STATE 1, 2 and so on (depending on NSTATE vaue)? I mean are these the S0 vibrational levels now (because now we are studying de-excitation)? If yes, then how exactly do I find the emission wavelength? Is the analysis similar to the absorption spectra analysis then? I mean using osc. str. etc.? Please guide me.
>>Also if Kasha's rule holds good, then do I get a high osc. str. at 1st excited state itself in the o/p file?

>>Regards,

>>On Thu Sep 25 '14 1:42am, Pavlo Solntsev wrote
>>----------------------------------------------
>>>Kasha's rule doesn't always work. For example, if you have redox active group near chromophore.

>>>Try to figure out absorbtion--emission situation for a porphyrin.

>>>-Pavlo.
>>>
>>>
>>>
>>>On Wed Sep 24 '14 9:11pm, Siddheshwar Chopra wrote
>>>--------------------------------------------------
>>>>Dear users,
>>>>Somebody please help me in understanding this concept. I need to know that by setting istate =1 in emission spectra calculation, I am actually setting or calculating the de-excitation from the S1 state. Am I correct? If yes, then the TDDFT o/p gives me a set of transitions possible for every excited state (set by variable nstate).What are these nstates now? Do they hold any significance in S1-->S0 transition? Do we mean that these are the vibrational levels of S0 level? Please explain this in the light of kasha's rule.
>>>>I am worried because I am unable to point out the emission wavelength. Please help me Alex Sir and Pavlo Sir. Please help me in analysing the emission calculations.

>>>>Kind Regards,
>>>>
>>>>
>>>>n Tue Sep 23 '14 12:21pm, Siddheshwar Chopra wrote
>>>>---------------------------------------------------
>>>>>Dear Users,
>>>>>Please have a look at the attached file which contains a table describing the contributions/transitions from first four states only for both the absorption and emission calculations. For absorption, I understand that the final state can be any of the excited states which has highest osc. strength. Am I right? But my doubt is regarding kasha's rule... If you see the emission data, the first excited state has a very low oscillator strength of 0.004 (HOMO-->LUMO(97 at 2678.9 nm. However the higher states have a better contribution than this state. So please tell me how to analyse this properly. To my knowledge emission wavelength is around 600-730nm.
>>>>>I would be grateful for any help.

>>>>>Kind Regards,


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