# Emission and absorption UV-Visible spectrum using GAUSSIAN-09

I am currently studying the UV-visible spectrum of ethylene using GAUSSIAN-09. I optimized the ground state(# opt b3lyp/6-31g geom=connectivity) then used the logfile to calculate the energy without optimizing it (# td=(root=10) b3lyp/6-31g geom=connectivity), but when I get the UV-visible spectrum from the log-file using Gaussview I do not know whether it is an absorption or emission spectrum, how can I distinguish between the two from my results?

When I try to run an optimization on the excited-state(#p opt freq=savenm td=(nstates=6,root=1) rb3lyp/6-31g(d) geom=connectivity), I get an error (Error termination request processed by link 9999). What causes this error? How can I solve it? And is it necessary to optimize the structure in the excited state to have the UV-visible spectrum?

How can we generate an absorption spectrum and an emission spectrum separately using GAUSSIAN09? What keywords do we have to add?

Can you recommend articles, books, or tutorials about GAUSSIAN software?

• +1 Welcome to Matter Modelling SE! Please note that you can render codes with backticks like this:  . Also note the formatting edits. About your question, I think Gaussiview should be able to show both absorption and emission spectra. And please also consider uploading the output file because it is difficult to understand what's going wrong with just an error code. – S R Maiti Jun 15 at 14:13
• Thank you for your comment and for welcoming me into Matter Modeling. – sarah bnm Jun 15 at 19:29