Dissociation energies of the I(3/2g) and I(1/2g) states of Ar+ 2

Rotationally resolved pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of 40Ar2 and 36Ar2 have been recorded between 124650cm−1 and 127 150cm−1 following resonant two-photon excitation via the 0+ u (v1= 0) Rydberg state located below the Ar (1S0) + Ar∗((3p)54s′ [1/2]1) dissociation limit. Four overlapping vibrational progressions were observed and attributed to transitions to the I(1/2u) u+ = 35–50, I(3/2g) u+ = 0–10, I(1/2g) v+ = 0–6 and I(3/2u) v+ = 0–2 vibronic states of Ar+ 2. The vibrational quantum numbers of the ionic states were derived from an analysis of the isotopic shifts, and the dissociation energies of the I(3/2g) (D+ 0(40Ar+ 2:) = 1509.4 ± 1.2cm−1) and the I(1/2g) (D+ 0(40Ar+ 2) = 616.3 ± 1.2cm−1) states were determined.