Formaldehyde valence excitation energies

Valence excitation energies for formaldehyde [36]. The second example is the GMC-QDPT calculation of valence excitation energies for formaldehyde molecule. Calculations on formaldehyde were carried out at the ground state experimental geometry (i.e. r(CO) = 1.203 A, r(CH) = 1.099 A, and 0(HCH) = 116.5°). The basis set used was Dunning s cc-pVTZ. 

CHjCHO Acetaldehyde is the prototype species for a wide variety of aliphatic carbonyl compounds. The photochemistry and electronic spectroscopy have been reviewed by Lee and Lewis The electronic structures in the carbonyl group of acetaldehyde are similar to those of formaldehyde in that the low lying valence and Rydberg levels have about the same energy. For example, n k excitation in both species gives rise to a weak absorption at 350-250 nm. The first Rydberg n - 3s excitation is found as a line-like feature at 182 nm, compared to the 174 nm band of CHjO. 

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