A Simultaneous Fit Of The Torsion-wagging-rotational Levels From The Excited (v_t = 0, 1 And 2) States Of Methylamine Using A Hybrid (tunneling And Non-tunneling) Hamiltonian Formalism

We used our hybrid program\footnote{I. Kleiner and J. T. Hougen, J. Mol. Spectrosc., 368, 111255 (2020)} to fit an extended dataset consisting of almost 30000 rotational-torsionial-wagging transitions in the MW and FIR of v$_t$ = 0, 1 and 2 of \chem{CH_3NH_2}. The program can fit rotational levels in molecules with one \chem{CH_3} internal-rotation large-amplitude motion, one \chem{NH_2} inversion large-amplitude motion. Our data set contains around 3000 MW and 26848 FIR transitions, which are fit to a weighted standard deviation of 1.75 using 102 parameters. Most of the FIR transitions are taken from recent measurements of the v$_t$ = 1-0 band centered near 265 cm-1\footnote{I. Gulaczyk, M. Kreglewski, V.-M. Horneman, J. Mol. Spectrosc. 342 (2017) 25-30}, and the ground torsional state transitions are from Motiyenko et al.\footnote{R.A. Motiyenko, V.V. Ilyushin, B.J. Drouin, S. Yu, L. Margulès, Astron.Astrophys. 563 (2014) A1}. Around new 340 and 176 microwave transitions were also assigned in the v$_t$ = 1-1 and v$_t$ = 2-2 states respectivelly. We hope to be able to fit all this data simultaneously with the far-infrared data from v$_t$ = 2-1, 2-0 and 2-2\footnote{Part of this work has been funded by the Programme National de Physique Chimie du Milieu Interstellaire (PCMI) and French ANR Labex CaPPA through the PIA under Contract No. ANR-11-LABX-0005-01}