Stimulated emission pumping spectroscopy of ²Σ and ²π vibronic levels in [Xtilde](v₁v₂0) ²π NCO

Abstract

We report measurements of ²Σ symmetry rovibronic levels in the (υ ₁, υ ₂, υ ₃)= (110)/(030) Fermi-resonant polyad and the 040 μ ²π states of NCO. The levels were detected by the technique of stimulated emission pumping spectroscopy in a supersonic free jet expansion following excitation of rotational lines in the Ã(100) ²Σ⁺−[Xtilde](000) ²π transition of the radical. Combining the new measurements and previously published data we have a complete set of experimental data for ²Σ and ²π vibronic levels of [Xtilde](v₁v₂ 0) ²π NCO for v ₁⪯2, v ₂⪯4 and for the (010) ²Δ vibronic states. A fairly complete effective Hamiltonian is described and the parameters in it are fitted to a sample representative of all these data. We successfully fit the data to close to the experimental measurement accuracy and derive a unique set of harmonic and anharmonic vibrational terms. The results are interpreted in terms of the electronic structure and vibrational potential energy surface of the radical.