High-resolution emission spectroscopy of the A2Π-X2Σ+ system of AlH+

► We investigate the emission spectrum of the A2Π-X2Σ+ transition of the AlH+ molecule. ► The full rotational structure of the 0-0 and 1-1 bands is observe and analyze. ► The breaking-off in the intensity of rotational lines of the 0-0 band at J″ = 36.5 is due to the dissociation phenomena in the X2Σ+ state of AlH+. ► Molecular constants is determine for the X2Σ+ state. ► An anomalous Λ-doubling of the A2Π state is the result of an interaction with unstableness rotational levels of X2Σ+ state and perturbing of the A2Π state by the nearly lying B2Σ+ state.