Lowest overtone and combination levels of DCCI: The Fermi resonance nu(3)=1/nu(5)=2

The infrared spectrum of deuterated monoiodoacetylene DCCI in the region of 220-550 cm(-1) has been studied at a resolution of 0.0020 cm(-1). The hot bands v(3) <-- v(5)(1) and 2v(5)(0,2) <-- v(5)(1) have been analyzed by con sidering especially the Fermi resonance v(3) = 1/v(5) = 2. In the next laye r of the hot bands (v(3) + v(5))(1) <-- v(3), (v(3) + v(5))(1) <-- 2v(5)(0. 2) and 3v(5)(1.3) <-- 2v(5)(2) the same Fermi resonance appears between v(3 ) = v(5) = 1 and v(5) = 3. In addition, various I resonances at the overton e levels have been considered. As a result, the vibrational and rotational constants for the level systems v(3) = 1/v(5) = 2 and v(3) = v(5) =1/v(5) = 3 together with the resonance parameters have been obtained. (C) 1999 Acad emic Press.