Interatomic potential of the HgNe van der Waals complex in the E( ³Σ⁺) Rydberg state

The lowest Rydberg state E(³Σ⁺) of the HgNe van der Waals complex has been investigated by optical-optical double resonance (OODR) spectroscopy using two intermediate electronic states of A ³O⁺ and B³1. The E-B band exhibits an oscillatory free-bound continuum, which reflects a Franck-Condon projection of the wave function of the B state onto the repulsive part of the E state potential. In the E-A band, two relatively sharp peaks are observed together with a free-bound continuum showing an asymmetric interference structure. The observed intensity patterns of the E-B and E-A bands are interpreted by a potential barrier characteristic of the E state potential, which traps two quasibound vibrational states in the inner well. Based on (i) the observed Franck-Condon pattern of the free-bound transitions; (ii) the transition's wave number of the bound-bound transitions in the E-A band; and (iii) the rotational constants of the quasibound (v=0 and v=1) levels in the E state, the interatomic potential of the E state is derived by a numerical simulation. The height of the potential barrier measured from the dissociation limit of Hg (7 ³S₁)+Ne is determined to be 153 cm^-1 and the interatomic distance at the top of the barrier to be located at 3.9(1) Å.