[CHM 331] Electronic Transitions in Polyene Aldehydes

[Andrew J. Pounds]

The computational chemistry capsule exercise on calculating UV 
transitions is one of my favorite.  As you have seen, oftentimes to get 
useful information out of Gaussian you have to do several things.  That 
is the case here as well.  On Friday I showed you a way to get the 
minimum energy to break the O-O bond in hydrogen peroxide.  An actual 
electronic transition that went to a dissociative well would in all 
likelihood take even more energy. What about the amount of energy 
required just to cause an electronic excitation.  Remember, there are 
lots of different ways to electronically excite a molecule and each 
different excitation results in different excited state potential curves.

In these systems we focus on just the HOMO and LUMO.  As directed, do a 
minimization, then look at the MO's in the output file.  RECORD THE 
NUMBER OF THE HOMO AND LUMO as well and if they are $\sigma$, 
$\sigma^*$, $\pi$, $\pi^*$. You must record the number of the orbital 
because that is the only reference you will have to find it in the next 
step.

Using your optimized geometry do the ZINDO calculation and follow the 
directions as indicated.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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