Observation of the C–H stretching band of methyl iodide dimer by infrared cavity ring-down spectroscopy

The infrared spectrum of dimeric methyl iodide produced in a supersonic jet has been re-measured in the C–H stretching region by cavity ring-down spectroscopy with higher resolution, 0.03 cm−1. Two absorption bands of the dimer, which could not be observed in our previous study [F. Ito, T. Nakanaga, Y. Futami, M. Nakata, Chem. Phys. 286 (2003) 337], have been identified. Analyses including peak decomposition and contour simulation have led to the assignment of the two bands to the head-to-head and head-to-tail isomers of (CH3I)2.