Properties of the transitions in the CH molecule model. Top panel: distribution of line strengths in the entire CH system. Only transitions with strengths greater than S = –5 were included in the NLTE model molecule. Bottom panel: X–A spectrum of the CH molecule around the wavelength of ~4300 Å. The P, Q, and R branches are indicated. The strongest feature in this range, corresponding to J′ − J″ = 0 (vibrational transition accompanied by a rotational transition) is the astrophysically famous 'G band'.