Two-photon spectroscopy at ultrahigh resolution: Fine structure and hyperfine structure of the (3sσ)A 2Σ+(v=1,N=3) Rydberg state of NO

The utility of ultrahigh resolution, continuous-wave laser sources in multiphoton spectroscopy is demonstrated by measurements of fluorescence excitation spectra resulting from two-photon pumping of individual rotational branches of (3sσ)A 2Σ+(v′=1,N′=3)←X 2Π(v′=0) NO. The general physical significance of fine structure and hyperfine structure interactions is briefly discussed emphasizing their relation to dynamical phenomena. Current observations yield the following fine structure and hyperfine structure parameters characterizing A(v=1,N=3) NO: γ=−80.10±0.04 MHz, b=40.9±0.2 MHz, c=1.5±4.5 MHz, and eQq=−7.2±0.5 MHz. The effective cross section for two-photon excitation of R11(J″=2.5) is estimated from experimental observables to be 1×10−44 cm4 s.