**Wavelengths and energy levels of molecules** __Question:__ The program calculates the energy levels of molecules, can it calculate the differences of these levels and display in the form of wavelength? I need to find the absorbtion/emission lines of molecules.

Can you please send me some information about the program or the user's guide so I can understand exacly how this software can help me.

Thank you.

__Answer:__ First I am going to refer you to the theory. It is a good idea to have a good understanding of the Huckel MO theory.

http://www.jce.divched.org/JCEDLib/LivTexts/pChem/JCE2005p1880_2LTXT/QuantumStat
es/Bookfolder/L21Huckel_MO_Theory.htm If you read the material carefully you will understand that the energy levels presented as the outcome of the calculation are in the form of alpha + e * beta, where e is the energy of the level that the program gives.

The wavelengths you can calculate as the differences between the energy levels. Note that Huckel theory only deals with the pi electrons so you can only calculate the wavelengths for those transitions (if allowed). The wavelength will then also be a value that contains the alpha and beta parameter values. You may be able to find emperical or calculated values for these parameters in the literature.