Effects of Cooper minima in resonance enhanced multiphoton ionization-photoelectron spectroscopy of NO via the D ^2Σ^+ and C ^2Π Rydberg states

Cooper minima are predicted to occur in the 3pσ→kσ(l=2) and 3pσ→kπ(l=2) channels in the resonance enhanced multiphoton ionization of NO via the D ^2Σ^+(3pσ) Rydberg state. The low energy kσ(l=2) Cooper minimum leads to the observed ΔN = N^+ − N’=0 photoelectron peak, in addition to the ΔN = ±1, ±3 peaks seen in the rotational spectra. The Cooper minima are accompanied by significant l mixing in the continuum due to the nonspherical molecular potential and result in a strong dependence of rotational branching ratios and angular distributions on photoelectron kinetic energy. A Cooper minimum is also predicted in the 3pπ→kδ(l=2) channel for photoionization of the C ^2Π(3pπ) Rydberg state. The effect of this Cooper minimum on photoelectron spectra and photoelectron angular distributions is also investigated