High-Resolution Infrared Spectrum of Monoiodoacetylene Between 2000 and 3000 cm-1.

The high-resolution infrared spectrum of monoiodoacetylene measured with a Bruker IFS 120 HR Fourier transform spectrometer in the spectral range of 2000-3000 cm-1 has been studied in detail. The strongest bands observed in the wavenumber region investigated are the C-C stretching fundamental nu2 (2034-2082 cm-1) and the accompanying hot bands of the types nu2 + nun - nun, where n = 3, 4, or 5, associated with the lowest stretching state v3 = 1 and with the low-lying bending states v4 = 1 and v5 = 1, 2, respectively. The combination bands of the types nu2 + nun, where n is as above, starting direct from the ground state have also been observed. In addition, the weak overtone band 2nu2 (4081-4121 cm-1) has been measured to study the anharmonicity of the C-C stretching mode. The new, more accurate values for the ground state rotational constants have been derived by combining the ground state combination differences calculated from our IR data available in the present work as well as in our previous investigations concerning the HCCI molecule to the accurate MW transitions from the literature. The rotational structures of the overtone level v2 = 2 and the combination levels v2 = vn = 1, where n is as above, have been investigated by analyzing the observed spectra with a model including various Fermi- and l-type resonances. As a result, the values for the harmonic frequency omega02 and the anharmonicity constants x22, x23, x24, and x25 are determined. Copyright 1998 Academic Press.