1. In our work with four‐membered‐ring molecules of presumed C2υ symmetry, the species B1 has been denned as that whose vibrations are symmetrical with respect to the plane of the ring and antisymmetric to the other plane. Previous workers2,3 with cyclopentene have defined the B2 species in this way. To avoid confusion we have adopted the latter convention in this paper.
2. C. W. Beckett, N. K. Freeman, and K. S. Pitzer, J. Am. Chem. Soc. 70, 4227 (1948).JACSAT0002-7863
3. S. S. Butcher and C. C. Costain, J. Mol. Spectry. 15, 40 (1965).JMOSA30022-2852
4. A. Danti, W. J. Lafferty, and R. C. Lord, J. Chem. Phys. 33, 294 (1960); JCPSA60021-9606
5. W. J. Lafferty, Ph.D. thesis, M.I.T., 1961.