Abstract Double charge transfer spectra of NO2+ were observed using 1.5-keV H+ projectiles. The vibrational progression of the X 2 Σ + state was resolved. For the unresolved vibrational peaks of the A 2 Π state, peak-fitting procedures determined their energies and intensities. From the present observation, the ν=0 energy of the A 2 Π state given by threshold photoelectrons coincidence method was corrected, which confirmed the independent recent work by Eland et al. This correction was concluded from the smooth vibrational distributions, suggesting the Franck–Condon behavior. So Franck–Condon analyses were performed to deduce the bond lengths for the X 2 Σ + and A 2 Π states, in a similar manner developed for photoelectron spectroscopy. For the X 2 Σ + state, the error of the bond length thus estimated is 0.005 A compared with the rotational data. For another quantitative check, high-level ab initio calculations have also been done. The theoretical Franck–Condon profiles well reproduced the experimental spectra, verifying the validity of the Franck–Condon principle.