The lowest-lying Rydberg state of CdAr van der Waals complex: The improved characterization of the interatomic potential

•Shape of the shallow outer well and potential barrier of the double-well E3Σ1+63S1 state in CdAr molecule experimentally determined.•υ′-assignment of the E3Σ1out+υ′←B3Σ1+υ″ transitions corrected and new values of vibrational constants for the outer well determined.•Determination of the E3Σ1out+ - state outer-well Re′out equilibrium distance improved.•Height Eb, position Rb, and shape of the potential barrier of the E3Σ1+ state estimated based on free ← bound E3Σ1+←B3Σ1+υ″ excitation spectra.