Line strengths of N_2O in the 1120–1440-cm^−1 region

Line strengths of N2O and its rare isotopic derivatives have been measured in the 1120–1440-cm−1 spectral region. The spectra were obtained at low sample pressure and high resolution (0.0054 cm−1), and the data are analyzed to determine band strengths, rotationless dipole moment matrix elements, and F factor coefficients for the various bands. First-order nondegenerate perturbation theory was used to derive explicit expressions for the rotationless dipole moment matrix elements and F factor coefficients, and from this derivation, general expressions for the F factor are obtained: F = [1 + a1m + a2J′(J′ + 1) + a3J″(J″ + 1)]2 for Δl = 0, ±1 bands and F = (1 + a1m)2 · H for Δl = ±2, ±3 bands, where H is given to good approximation for |Δl| = 2 bands as H = [J′(J′ + 1)]2. These F factor expressions are applied in the analysis of the experimental data from which the vibrational band strength of the forbidden band 0220(e)–0000 was found to be (5.69 ± 0.26) × 10−8 cm−2/atm at 296 K. The theoretical results can also be applied to CO2 line strengths.