Detailed analysis of ν5 of CH3I: Fermi and Coriolis resonances with ν3+ν6 and ν2

The high‐resolution infrared spectrum of ν5 of CH3I reported in the previous paper [J. Chem. Phys. 55, 1787 (1971)] has been reanalyzed. By extending the assignment of the observed lines and by taking account of the xy‐type Coriolis interaction with ν2 in addition to the Fermi and xy‐type Coriolis resonances with ν3+ν6, the rotational constants have been determined to be B 5(unp) = 0.250159 cm−1 and B 3,6(unp) = 0.247631 cm−1 which are now consistent with the microwave results. The l‐type doubling constant has been obtained to be q 5(unp)=−2.2× 10−5 cm−1. The Fermi resonance term has been found to depend on the quantum number J.

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