Some Raman bands of C3O2

The ν₁, ν₅, 2ν₅, and 2ν₆ Raman band accumulations of carbon suboxide, C₃O₂, have been photographed with a resolution of 0.2–0.3 cm^?1. Each band accumulation consists, in addition to the main band, of a large number of “hot” bands due to the extremely low, highly anharmonic ν₇ fundamental vibration. In the 2ν₆ band accumulation a few series of unresolved Q branches have been assigned. In the ν₁ and 2ν₅ band accumulations most Q branches almost coincide, forming a very intense peak, whereas the dominating feature of the ν₅ band accumulation is a minimum, in agreement with the expectation of an extremely weak Q branch for a Π_g fundamental band. Tentative values of ν₁ = 2196.9 ± 0.1 cm^?1 and ν₅ = 580.2 ± 0.5 cm^?1 as well as several energy values in the ν₇ manifold of the 2ν₆⁰ state are obtained. Further, improved exposures of the ν₂ + 2ν₇⁰ band accumulation yield some levels in the ν₇ manifold of the ν₂ state, in addition to those determined previously.