Observation of double-well potential of NaH C ¹Σ⁺ state: Deriving the dissociation energy of its ground state

Vibrational levels (v = 6-42) of the NaH C ¹Σ⁺ state including the inner and outer wells and the near-dissociation region were observed by pulsed optical-optical double resonance fluorescence depletion spectroscopy. The absolute vibrational quantum number is identified by comparing the vibrational energy difference of this experiment with the ab initio calculations. The outer well with v up to 34 is analyzed using the Dunham expansion and a Rydberg-Klein-Rees (RKR) potential energy curve is constructed. A hybrid double-well potential combined with the RKR potential, the ab initio calculation, and a long-range potential is able to describe the whole NaH C ¹Σ⁺ state including the higher vibrational levels (v = 35-42). The dissociation energy of the NaH C ¹Σ⁺ state is determined to be D_e(C) = 6595.10 ± 5 cm^-1 and then the dissociation energy of the NaH ground state D_e(X) = 15 807.87 ± 5 cm^-1 can be derived.