# A Variationally Computed IR Line List for the Methyl Radical CH$_3$

## TL;DR

This paper introduces the first variational ab initio line list for the CH₃ radical, enabling accurate modeling of its spectral properties at high temperatures up to 1500 K.

## Contribution

It provides a comprehensive, high-accuracy line list for CH₃ based on variational calculations using a high-level potential and dipole moment surface.

## Key findings

- Line list contains over 9 million ro-vibrational states.
- Excellent agreement with experimental vibrational energies and intensities.
- Suitable for modeling spectra at temperatures up to 1500 K.

## Abstract

We present the first variational calculation of a hot temperature ab initio line list for the CH$_3$ radical. It is based on a high level ab initio potential energy surface and dipole moment surface of CH$_3$ in the ground electronic state. The ro-vibrational energy levels and Einstein $A$ coefficients were calculated using the general-molecule variational approach implemented in the computer program TROVE. Vibrational energies and vibrational intensities are found to be in very good agreement with the available experimental data. The line list comprises 9,127,123 ro-vibrational states ($J\le 40$) and 2,058,655,166 transitions covering the wavenumber range up to 10000 cm$^{-1}$ and should be suitable for temperatures up to $T= 1500$ K.