High-resolution infrared and millimeter-wave spectroscopy of CH35Cl3…

The v2=v6 = 1 (∼936.5 cm−1) vibrational level of chloroform CH35Cl3 has been studied for the first time by high-resolution FTIR and millimeter-wave spectroscopy. Like the v6 = 1 and v3=v6 = 1 vibrations, the v2=v6 = 1 level is characterized by an exceedingly small value of |C − B − Cζ| ≈ 2.88  × 10−3 cm−1. Hence, a global l(2,2) resonance connects the (k − 1, l6 = −1) and (k + 1, l6 = +1) sublevels. This quasi-generalized l(2,2) resonance is almost exclusively responsible of the appearance of the ν2 + ν6 combination band, with its Q-branches falling in a narrow region close to the band origin, together with its, partially resolved, clusters of K-lines on the P and R sides of the spectrum, for each value of J.