Two-photon spectroscopy of Rydberg states of NO

Abstract
Two-photon spectroscopy of supersonically cooled NO in the region between the NO+ X 1Σ+, v+=0 and 1 ionization thresholds reveals the n=7–12 members of the ndπ−, v=1 Rydberg series. The n=5 member of the same series is observed below the two-photon ionization threshold by using two-photon resonant, three-photon ionization. The data are analyzed by using multichannel quantum defect theory to extract rotationless quantum defects and to reveal perturbation by the nf, v=1 series. Theoretical two-photon rotational line strengths are in satisfactory agreement with the observed data.