An exploration of the vacuum ultraviolet magnetic circular dichroism and absorption spectra of propylene
and a comparison to ethylene spectra provides new information on the electronic structure of ethylene. Ethylene
has three electronic transitions in the energy region previously assigned as two. The presently proposed
assignments for these transitions are π → 3s(1Ag → 1B3u), π → π*(1Ag → 1B1u), and π → 3p. The lowest
energy transition that was previously assigned as the beginning of the π → π* is assigned as the π → 3s
transition. The π → π* and π → 3p transitions are accidentally degenerate in ethylene. The electronic transition
with sharp structure doublets which was previously assigned as π → 3s is assigned as one of the π → 3p [π
→ 3pσ (1Ag → 1B2g), π → 3p
y
(1Ag → 1B1g), or π → 3p
x
(1Ag → 1A1g)] vibronically allowed electronic transitions.
A case is presented that it is the π → 3pσ (1Ag → 1B2g) and/or the π → 3p
y
(1Ag → 1B1g) electronic transitions
that are responsible for the sharp structured doublets in ethylene.
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