High-order multiphoton ionization photoelectron spectroscopy of NO

Photoelectron energy angular distributions of NO following three different high-order multiphoton ionization (MPI) schemes have been measured. The 3 + 3 resonantly enhanced multiphoton ionization (REMPI) via the A2Σ+ (v=O) level yielded a distribution of electron energies corresponding to all accessible vibrational levels (v+=O-6) of the nascent ion. Angular distributions of electrons corresponding to v+=O and v+=3 were significantly different. The 3 + 2 REMPI via the A2Σ+ (v=1) level produced only one low-energy electron peak (v+=1). Nonresonant MPI at 532 nm yielded a distribution of electron energies corresponding to both four- and five-photon ionization. Prominent peaks in the five-photon photoelectron spectrum (PES) suggest contributions from near-resonant states at the three-photon level. 4 refs., 3 figs