High-Resolution Coherent Raman Spectra of Vibrationally Excited 14N2 and 15N2

At an effective resolution of 0.001 cm-1, we measured coherent anti-Stokes Raman spectra of electrically discharged 14N2 and 15N2 in the electronic ground state X1Sigmag+, specifically Q branches of bands with Deltav = 1 up to v' = 8 for 14N2 and v' = 7 for 15N2, and O and S branches of the fundamental band of 15N2. Account is taken of small wavenumber shifts due to pressure, AC Stark, and |chi|2 interference effects. Separate fits of the Q-branch data of each isotopic variant, combined with selected data from the literature, yield term coefficients Ykl and Ukl or potential-energy coefficients cj that reproduce wavenumbers of measured spectral lines generally within 0.004 cm-1. The value of the harmonic vibrational parameter omegae is 2358.5402(4) cm-1 for 14N2 and 2278.7913(7) cm-1 for 15N2. Efforts to combine spectral data of both isotopic variants to distinguish adiabatic and nonadiabatic effects arising from incomplete separation of electronic and nuclear motion in N2 were unsuccessful. Copyright 1997 Academic Press. Copyright 1997Academic Press