Coherence-converted population transfer FTMW-IR double resonance spectroscopy of CH3OD in the OD-stretch region

Rotationally selected infrared spectra of jet-cooled CH3OD have been recorded and analyzed in the OD-stretch region (2710-2736 cm−1). The observed spectra are obtained by monitoring three E-species microwave transitions (1−1 ← 10 at 18.957 GHz, 2−1 ← 20 at 18.991 GHz, and 3−1 ← 30 at 19.005 GHz) in a narrowband cavity Fourier transform microwave spectrometer, using the background-free coherence-converted population transfer technique. Of the four upper state subbands observed, two (K′ = 0 and −2) are split by perturbations. The E-species deperturbed band origin is at 2718.1 cm−1. The deperturbed reduced term values follow a pattern similar to the ground state. This allows the J′ = 0 torsional tunneling splitting to be estimated as 2.1 cm−1, which can be compared to 2.6 cm−1 in the ground state.