Dear anjali,

You no need to worry abou the positive and negative energies obtained. The mentioned transitions from the mentioned orbitals is with the oscillator strength of 0.00 and excitation energy of 2.9455 and its wavelength is 420 nm.

If you have any further queries, mail me ur files at [email protected].

Best wishes to you.....

Dear Sir,

Thank you very much for your answer. 

Dear Anjali,

I think Venkatesan is right and I wana add few more points..

Oscillatory strength is related to the intensity of the peak and 82 --> 93 etc  represents the transitions. If you will look into Khon-Sham orbitals you will be able to trace out from where the electron density shifts and you will come to know the type of transition i,e pi-pi or mlct etc.

Dear Mohsin,

Thank you very much for the reply.

But, how I can find out the Khon-Sham orbitals and use it to obtain the required information? 

Please excuse me for this silly question, but actually I am not sure about that thing.

Dear Anjali,

G. LIang has rightly and  clearly explained your quire and in fact generating MO"s is not a big deal. Born one thing in mind don't compare the wrong orbitals. Let me tell U no question is silly its just the matter of time.

Lots of luck.

Hi, You can also use GaussSum to get the spectra as well as contributions of transition in each excitation.

Dear Anjali Sunilkumar,

the composition of the B3LYP orbitals should be reported in the SCF part of the output.

In any case, you can plot the isosurfaces of any orbitals using the Gaussian's starting from the .chk file using the utilities cubegen and formchk.

Hi Anjali,

         First you have to confirmed theoretical UV  lamda max value, and then correlated with results of you have. commonly we know simple absorption maxima unconjucated chromophores, 420 nm means n-pi * transition may occur in C=O, C=N. and then find contribution.