High‐resolution Fourier transform Raman spectra of the fundamental bands of ¹⁴N¹⁵N and ¹⁵N₂

The Fourier transform Raman spectra of the fundamental bands of 14 N 15 N and 15 N 2 were measured with a resolution of 0.02 cm −1 . Lines from all branches (O, Q, S) were observed and measured. The analyses of the wavenumbers yield improved values for the band origins ν 0 ( 14 N 15 N) = 2291.33773(8) cm −1 and ν 0 ( 15 N 2 ) = 2252.07846(9) cm −1 and improved values for the rotational parameters of the ground state and the first excited state of the two molecules. The values obtained for 14 N 15 N are B 0 = 1.9236102(35) cm −1 and D 0 = 5.3530(94) × 10 −6 cm −1 and B 1 − B 0 = −0.01651064(86) cm −1 and D 1 − D 0 = 1.06(16) × 10 −8 cm −1 . For 15 N 2 the following values obtained are B 0 = 1.8576250(36) cm −1 , D 0 = 4.9760(87), B 1 − B 0 = 0.01566657(99) cm −1 and D 1 − D 0 = 0.94(18) × 10 −8 cm −1 . The bond length calculated for all three isotopomers of molecular nitrogen shows a systematic decrease with increasing molecular mass.