Adiabatic ionization potential of Al2 and vibrational spectrum of the X 2Σ+g state of Al+2

Abstract

We have measured the adiabatic ionization potential of the aluminum dimer, AIP(Al₂)=5.989±0.002 eV (±2σ uncertainty), using threshold photoelectron spectroscopy with resonant two photon ionization (ω₁ fixed and ω₂ scanned). We obtain the Al⁺₂ , X ²Σ⁺_g vibrational constants ω_e =178±8 cm⁻¹ and ω_ex_e =2±2 cm⁻¹ (±2σ uncertainty), the first spectroscopic data for a cationic Al cluster. These results are in excellent agreement with ab initio calculations.