An Updated Infrared Solar Spectrum from ACE-FTS and a CH Rovibrational Line List

An updated Atmospheric Chemistry Experiment Fourier Transform Spectrometer infrared solar spectrum has been produced from low-Earth orbit covering 1829–4440 cm−1 (2.252–5.467 μm). Spectroscopic constants for the v = 4 and v = 5 vibrational levels of the X2Π state of CH radical have been updated by incorporating additional vibration–rotation lines from the new solar spectrum and from an archival laboratory spectrum. New ab initio calculations of the permanent dipole moment function for the X2Π state were performed with the MOLPRO quantum chemistry package using the internally contracted multireference configuration interaction method. This dipole moment function, along with the equilibrium constants calculated in this work, was used in the LEVEL program to calculate line strengths. The effect of vibration–rotation interaction on line strengths, known as the Herman–Wallis effect, was taken into account. The resulting line strengths were compiled into a new line list, which will aid in determining the abundance of CH in diverse astrophysical environments.