Multiphoton ionization of nitrogen dioxide: Four photon spectroscopy of the n pσu Rydberg series

Abstract

Mass resolved multiphoton ionization (MPI) of NO₂ reveals resonance‐enhanced production of NO⁺₂ in the region from 490 to 540 nm. From an analysis of the MPI spectrum, we assign these resonant features to four photon transitions to high‐lying members of the npσ_u Rydberg series. A high resolution scan of one of these features shows clear rotational structure, the assignment of which yields a rotational constant for the linear upper state (B′=0.440±0.005 cm⁻¹).