Ab Initio Study of the Large Amplitude Motions of Various Monosubstituted Isotopologues of Methylamine (CH3-NH2)
Open Access
- 23 September 2021
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Chemistry
Abstract
CCSD(T)-F12 theory is applied to determine electronic ground state spectroscopic parameters of various isotopologues of methylamine (CH3-NH2) containing cosmological abundant elements, such as D, 13C and 15N. Special attention is given to the far infrared region. The studied isotopologues can be classified in the G12, G6 and G4 molecular symmetry groups. The rotational and centrifugal distortion constants and the anharmonic fundamentals are determined using second order perturbation theory. Fermi displacements of the vibrational bands are predicted. The low vibrational energy levels corresponding to the large amplitude motions are determine variationally using a flexible three-dimensional model depending on the NH2 bending and wagging and the CH3 torsional coordinates. The model has been defined assuming that, in the amine group, the bending and the wagging modes interact strongly. The vibrational levels split into six components corresponding to the six minima of the potential energy surface. The accuracy of the kinetic energy parameters has an important effect on the energies. Strong interactions among the large amplitude motions are observed. Isotopic effects are relevant for the deuterated species.Keywords
Funding Information
- Deanship of Scientific Research, King Saud University
This publication has 60 references indexed in Scilit:
- Torsion–Inversion Tunneling Patterns in the CH-Stretch Vibrationally Excited States of the G12 Family of Molecules Including MethylamineThe Journal of Physical Chemistry A, 2013
- General Perturbative Approach for Spectroscopy, Thermodynamics, and Kinetics: Methodological Background and Benchmark StudiesJournal of Chemical Theory and Computation, 2012
- Molecules atz= 0.89Astronomy & Astrophysics, 2011
- Atmospheric condensed‐phase reactions of glyoxal with methylamineGeophysical Research Letters, 2009
- Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functionsThe Journal of Chemical Physics, 1992
- Further resolution of the infrared amino wagging band of methylamineSpectrochimica Acta Part A: Molecular Spectroscopy, 1985
- Probable detection of interstellar methylamine-D /CH3NHD/The Astrophysical Journal, 1977
- Detection of Interstellar Methylamine by its 2_{02}->1_{10} A_{a^{-}} State TransitionThe Astrophysical Journal, 1974
- Detection of Interstellar MethylamineThe Astrophysical Journal, 1974
- Force Constants in Methylamine-A Determination by the Use of 15N Isotope ShiftsThe Journal of Chemical Physics, 1972