Extreme ultravioletϩultraviolet ͑XUVϩUV͒ two-photon ionization spectra of the b 1 ⌸ u (v ϭ0-9), c 3 1 ⌸ u (vϭ0,1), o 1 ⌸ u (vϭ0,1), c 4 Ј 1 ⌺ u ϩ (vϭ1) and bЈ 1 ⌺ u ϩ (vϭ1,3-6) states of 15 N 2 were recorded with a resolution of 0.3 cm Ϫ1 full-width at half-maximum ͑FWHM͒. In addition, the b 1 ⌸ u (vϭ1,5-7) states of 14 N 15 N were investigated with the same laser source. Furthermore, using an ultranarrow bandwidth XUV laser ͓ϳ250 MHz (ϳ0.01 cm Ϫ1) FWHM͔, XUVϩUV ionization spectra of the b 1 ⌸ u (vϭ0-1,5-7), c 3 1 ⌸ u (vϭ0), o 1 ⌸ u (vϭ0), c 4 Ј 1 ⌺ u ϩ (vϭ0), and bЈ 1 ⌺ u ϩ (v ϭ1) states of 15 N 2 were recorded in order to better resolve the band-head regions. For 14 N 15 N, ultrahigh resolution spectra of the b 1 ⌸ u (vϭ0-1,5-6), c 3 1 ⌸ u (vϭ0), and bЈ 1 ⌺ u ϩ (vϭ1) states were recorded. Rotational analyses were performed for each band, revealing perturbations arising from the effects of Rydberg-valence interactions in the 1 ⌸ u and 1 ⌺ u ϩ states, and rotational coupling between the 1 ⌸ u and 1 ⌺ u ϩ manifolds. Finally, a comprehensive perturbation model, based on the diabatic-potential representation used previously for 14 N 2 , and involving diagonalization of the full interaction matrix for all Rydberg and valence states of 1 ⌺ u ϩ and 1 ⌸ u symmetry in the energy window 100 000-110 000 cm Ϫ1 , was constructed. Term values for 15 N 2 and 14 N 15 N computed using this model were found to be in good agreement with experiment.
