[CHM 331] 2) iv

[Andrew J. Pounds]

On 11/15/2012 10:46 PM, wrote:
> Dr. Pounds,
> I was successful in getting the rigid scan to work for hydrogen 
> peroxide. I scanned 200 points from .5 to 10 Angstroms and got the 
> values out of the log file. I fit the Morse potential to this data and 
> got values of De, a, and Re.
>
> I thought that the energy needed to photolize the peroxide would be 
> the spectroscopic dissociation energy, Do, not De. I was planning to 
> use equation 13.80 and 13.83 to calculate Do but I ran into a problem, 
> equation 13.83 requires a reduced mass which i did not know how to 
> compute for hydrogen peroxide.
>
> Next I tried using De as the value and it produced a very large energy 
> (around 5.1 ev).
>
> I'm not sure what I should do from here.
>
>

To photolytically dissociate the molecule along the O-O bond you will 
have to excite it to some electronic state (represented by a 
dissociative potential surface higher in energy than the one you are 
calculating).  However, you can approximate the minimum amount of energy 
that you need to dissociate the molecule by simply determining  the 
depth of the energy well (or De).

If we actually calculated the potential surface of the electronically 
excited state which was represented by the dissociative potential, we 
would have to do A LOT more work.  We would have to explicitly fix the 
electronic populations and spin states in each excited state we were 
following and then compute potential surfaces to find the one that leads 
to dissociation along the O-O bond.  Not something I think you guys are 
up for at this time.

On a side note -- when you do a ZINDO calculation it does some of this 
"population setting" to predict the vertical excitation energies to low 
lying electronic states.

-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://theochem.mercer.edu/pipermail/chm331/attachments/20121116/d20f6832/attachment.html>