The 39K2 2 3Σg+ state: Observation and analysis
Résumé
The 39K2 2 3Σg+ state has been observed by perturbation-facilitated infrared-infrared double resonance spectroscopy and two-photon excitation. Resolved fluorescence spectra into the a 3Σu+ state have been recorded. The observed vibrational levels have been assigned as the v=23-25, 27, 28, 31-33, 38-45, 47, and 53 levels by comparing the observed and calculated spectra of the 2 3Σg+-->a 3Σu+ transitions. Molecular constants have been obtained using a global fitting procedure with a comprehensive set of experimental data. Fine and hyperfine splittings have been resolved in the excitation spectra. Perturbations between the 2 3Σg+ and 2 3Πg states were observed. The hyperfine patterns of the 2 3Σg+ levels are strongly affected by the perturbation. The perturbation-free and weakly perturbed levels follow the case bβS coupling scheme, while the perturbed levels follow case bβJ coupling. A Fermi contact constant, bF=65+/-10 MHz, has been obtained. Intensity anomalies of rotational lines appeared both in the 2 3Σg+~2 3Πg<--b 3Πu excitation spectra and in the 2 3Σg+~2 3Πg-->a 3Σu+ resolved fluorescence spectra. These intensity anomalies can be explained in terms of a quantum-mechanical interference effect.