Context. The N2+ fluorescence spectrum of comet C/2016 R2 is modelled by Rousselot and coworkers (A&A in press). That work relies on accurate Einstein coefficients for electric dipole transitions between the B 2Σu+ and X 2Σg+ 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.