Perturbations, intensity anomalies, and line broadening of23Na39K studied by optical-optical double resonance polarization spectroscopy

The high resolution spectrum of the 23Na39K molecule in the 33 200-33 340 cm-1 region is measured by Doppler-free optical-optical double polarization polarization spectroscopy, and the F1Δ(vf + 4), K1Σ+(vk + 3), U1Π(vu - 1), and W3Π( w ) levels are studied. Intensity anomalies between P(J + 1) and R(J - 1) lines are observed for transitions to the K1Σ+(vk + 3) and U1Π(vu - 1) levels, and these are identified as a quantum mechanical interference effect. Energy shifts of the K1Σ+(vk + 3, J) levels centred at J = 39–40 and the U1Π(vu - 1, J) levels centred at J = 30–31 are observed, and these are identified as being caused by an additional interaction with the W3Π state. The line broadenings of the U1Π(vu - 1, J) levels centred at J = 35 are observed, and are identified as originating from the predissociation, which leads to two separated atoms K(5p) and Na(4s).