High resolution FTIR spectrum of cyanogen iodide between 200 and 5000 cm-1. Global rovibrational analysis of IR and MW data for I(12)C(14)N.

The infrared absorption spectrum of ICN has been recorded in the region 200–5000 cm−1 with a Bruker 120HR interferometer, and several tenthousands of lines have been measured with a precision between 0.0001 and 0.001 cm−1. Most of these lines have been assigned. These new data were combined with transitions previously measured in the microwave and millimeterwave ranges. After a band-by-band analysis including 292 subbands a rovibrational global analysis has been performed using all available data. The main resonances are the rotational l-type resonance and the strong Fermi resonance coupling the states ν1=1 and ν2=2 via the cubic anharmonic constant k122. In addition, many local resonances became evident by the observation of the corresponding avoided crossings. In particular, there is a direct coupling between the states (400) and (240) due to the fourth-order resonance k112222. There is also a fourth-order Coriolis resonance governed by C11222 responsible for interactions between the (200) and (030) states. All these interactions have been taken into account in one-step diagonalization procedures. A statistical agreement with the 6344 selected pieces of data has been obtained, with an estimated standard deviation =0.660. All those data and their deviations are given in the first depository. A set of 109 parameters including 24 off-diagonal anharmonic and Coriolis resonance parameters has been derived. They have been used to calculate effective rovibrational parameters for all substates up to more than 6000 cm−1, also listed in the second depository.