Observation of the nu(6)+nu(9) band of ketene via resonant coriolis interaction with nu(8)

We observed and analyzed a b-axis Coriolis resonance between higher J state s of the v(6) + v(g9) combination band and the v(8) fundamental of ketene i n the spectral region 940-970 cm(-1). The interaction resonantly couples K- a = 1 states of the combination band to K-a = 0 states of the fundamental a nd also affects K-a = 1, 2 states in the fundamental. Due to the involvemen t of strongly asymmetry-split low K levels, the rotational constants and ba nd origin of v(6) + v(9) could be accurately determined and are discussed i n the light of high-quality anharmonic force fields. The Coriolis coupling parameter, zeta(8.6+9)(b), is very precisely determined. A smaller perturba tion, which could not be fully analyzed, is tentatively attributed to K-a, = 2 upper states in the V-5 + v(9) band, (C) 1999 Academic Press.