Description

The lines of the 0+ and 0– states have been summarized by
(1) R. D. Brown, P. D. Godfrey, R. Champion, 1987, J. Mol. Spectrosc. 123, 93.
The C3O chain of the molecule is bent with a small barrier to linearity. Hence, there are two tunneling states. The 0– state is 0.1198 cm–1 higher in energy than the 0+ state. The a type transitions are within each substate, the b type transitions between the states. Because of the limitations of the data set, extrapolations beyond 100 GHz or beyond Ka larger than 5 or 1 for a and b type transitions, respectively, should be viewed cautiously.
At low temperatures, it may be necessary to discern between ortho-l-H2C3O and para-l-H2C3O. The ortho states are described by Ka odd and even for the 0+ and 0– state, respectively, the para states by Ka even and odd, respectively. The nuclear spin-weights are 3 and 1 for ortho-l-H2C3O and para-l-H2C3O, respectively. The JKaKc = 111 level is the lowest ortho and para level for the the 0+ and 0– state, respectively, It is 5.2597 and 5.3795 cm–1, respectively, above ground.
The dipole moment was determined in
(2) R. D. Brown, P. D. Godfrey, R. Champion, D. Mc Naughton, 1981, J. Am. Chem. Soc. 103, 5711.