Rydberg absorptions, structured, excitation

Excitation and dissociation via the structured Rydberg absorptions, /Iphoi < 124 nm... 

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. 

The longest wavelength absorption of 112 is centered around 54 000 cm This is a very weak band (e 10) and should be associated with the Ai(3e - 4e ) excited state. In solution the absorption then rises to a medium intense band at ca. 70 000 cm and reaches an intense maximum at ca. 83 000 cm Mn the gas phase two structured bands appear at 62000 cm and 76 000 cm According to equation 21 these bands result from 3e - 3p and 3e - 4p Rydberg transitions ((5 = 0.68). As expected for a Rydberg band the 62 000 cm band disappears going from the gas phase to the condensed phase. 

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