Relative intensities of the rotational lines of the (0, 0) and (0, 1) bands of the B2Σ+u-X2Σ+g systems of N+2

A high resolution grating spectrometer and a hollow-cathode lamp were used to study the relative intensities for lines of the transition B²Σ⁺_u→X²Σ⁺_g of the ion N⁺₂. Mulliken's formulae are obeyed with a precision of better than 2% for N^′?30, except for the first two lines, for which the relative intensities of the P lines are 2.5% greater than Mulliken's values and the relative intensities of the R lines 2.5% lower. The differences in the positions of the doublets for the first lines increase linearly (γ′?γ″=0.015±0.002cm^-1 with γ″≈0.010cm^-1) for N′?10. An interpretation of this difference gives an order of magnitude for the perturbation parameters of the state A²Π_u(v′=10)(ξ≈9cm^-1, η≈0.06cm^-1). The effect of this perturbation on the line intensities is negligible for N′?30.