Observation of the shallow 2Π1 state of NaH

The 2 1Π state of NaH has been observed up to the last bound vibrational level using pulsed optical-optical double resonance fluorescence depletion spectroscopy. A total of 20 rovibrational energy levels (v = 2–4 and J = 1–9) were assigned to this electronic state by means of comparing the successive rovibrational spectra to the eigenvalues of the ab initio potential energy curve. The decrease of background fluorescence near the atomic asymptotic limit Na(3d) + H(1s) is an indication of reaching the dissociation limit of the NaH 2 1Π state. Unobserved rovibrational levels (v = 0 and 1) are due to poor Franck-Condon overlap of 2 1Π ← A 1Σ+ transition within the accessible rovibrational levels of intermediate A 1Σ+ state of this work.