The conformation of acetaldehyde in its n→3s Rydberg state

The conformation of acetaldehyde in its n→3s Ryberg state is stated to be s–cis (one methyl hydrogen eclipsed by oxygen). Heath et al.1 stated on the basis of their measurements that it was not possible to tell whether this excited state was a s–cis. The calculations presented here definitely establish the excited state as a s–cis.(AIP)