2024MNRAS.52710726P

Comprehensive and accurate rovibronic line lists for the X ¹Σ⁺ and A ¹Π states of ¹²C¹H⁺ and ¹³C¹H⁺ which should be applicable up to temperatures of 5000 K are presented. Available empirical potential energy curves and high-level ab initio dipole and transition dipole moment curves are used with the program LEVEL to compute rovibronic energy levels and Einstein A coefficients. Λ-doubling is incorporated into the energy levels and A-coefficients involving the A ¹Π state using an empirical method. For ¹²C¹H⁺, line positions are improved by using both laboratory and astronomical observational spectra as input to the MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure. The ¹²C¹H⁺ line list contains 1505 states and 34 194 transitions over the frequency range of 0-33 010 cm^–1 (λ > 300 nm). Comparisons with observed astronomical and laboratory spectra give very good agreement. The PYT CH⁺ line lists and partition functions are available from the ExoMol database at www.exomol.com.