Accurate Einstein coefficients for electric dipole transitions in the first negative band of N2+

Context. The N₂⁺ fluorescence spectrum of comet C/2016 R2 is modelled in a companion paper. That work relies on accurate Einstein coefficients for electric dipole transitions between the B²∑_u⁺ and X²∑_g⁺ electronic states of N₂⁺.
Aims: These coefficients are provided in the present paper.
Methods: The potential energy curves and transition dipole moments were computed at a high level of ab initio theory and include relativistic corrections. Rovibrational wavefunctions were then obtained without assuming separability of vibrational and rotational motions.
Results: Vibrationally and rotationally resolved Einstein coefficients are presented in a convenient three-parameter functional form for three isotopologues. A possible explanation is given for the large variation in the experimental radiative lifetimes.