The anharmonic force field of nitrous oxide

The general sextic force field of nitrous oxide has been determined by matrix diagonalization (table 1, A). Comparison with previous force fields derived by the application of perturbation theory and contact transformation suggests that it represents the potential surface in the 0–9000 cm-1 range to about 5 per cent. Agreement between calculated and observed rotational parameters, q and D, confirms that the present scheme provides a more accurate means of calculation than perturbation theory. Attempts to reduce the number of force field parameters, while retaining an adequate description of the potential surface and fit to spectroscopic data, are equally successful whether the ρ or Я expansion coordinate is employed.