The first far-infrared high resolution absorption measurement of the cis-methyl nitrite molecule has been recorded in the range 15-400 cm -1 using the synchrotron AILES beamline radiation at SOLEIL with a resolution of 0.0011 cm-1. First assignments for the pure rotational transitions (15-65 cm-1) belonging to the ground νt (=ν15) = 0 and first νt = 1 excited torsional state are based on measurements from previous studies performed in the 13-40 GHz spectral range, as well as on new millimeter-wave measurements performed at Lille in the spectral range 75-465 GHz. A few measurements and remeasurements in the 1.8-13 GHz were also performed using the chirped FT-MW spectrometer located in North Texas. The pure rotational transitions in the far-infrared and in the microwave spectral range belonging to the two first torsional states have been globally fitted using the RAM ("Rho Axis Method") dealing with the rotation-torsion Hamiltonian and implemented in the BELGI code. A total of 708 and 713 microwave transitions (6 ≤ J ≤ 40, Kamax ≤ 23) belonging to the ground torsional state νt = 0 and 1 have been fitted with root-mean-square (rms) deviations of 37.4 kHz and 32.3 kHz respectively, and 3170 pure rotational transitions in the far-infrared range (12 ≤ J max ≤ 65, 0 ≤ Kamax ≤ 48) belonging to νt = 0 and 1 have been fitted with a rms deviation of 0.00017 cm-1, using 35 parameters. Since in the far-infrared spectral range, the A-E internal rotor splittings have not been observed for the transitions belonging to the torsional ground νt = 0 state of the cis-methyl nitrite species, another fit was performed on those lines, using a Watson type Hamiltonian for comparison.
Bibliographical noteFunding Information:
The authors wish to thank Dr. M. David for his assistance and advice during the preparation of the chemical synthesis of CH 3 ONO. The authors are deeply indebted to Dr Laurent Manceron for advices, discussions and helping with the recording of the methyl nitrite spectrum at the French synchrotron SOLEIL. J.-C. Guillemin thanks the PCMI (INSU-CNRS) for financial support. Part of this work is supported by the French ANR-08-BLAN TopModel grant.
- High resolution
- Internal rotation
- Line positions
- Methyl nitrite
- Rotation-torsion spectrum