Potential curve of the 41Σ+ state of NaK by polarisation labelling spectroscopy

The 41Σ+ state of NaK molecule has been observed for the first time and studied by polarisation labelling spectroscopy technique. A total of 1567 rovibronic levels in this state were measured with an accuracy better than 0.1 cm−1. The inverted perturbation approach method was used to construct the potential energy curve of the 41Σ+ state. The irregular shape of the potential confirms earlier theoretical predictions.