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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The full interaction potential between Ne( 1 S) and Ne ϩ ( 2 P) is determined by least-squares fitting of potential parameters to spectroscopic data, principally from the near-dissociation microwave spectra of the Ne 2 ϩ complex. The potential obtained in this way incorporates the potential curves for all six electronic states correlating with Ne( 1 S)ϩNe ϩ ( 2 P) and the couplings between them. Coupled-channel calculations on the potential take account of breakdown of the Born-Oppenheimer approximation and provide an accurate description of the microwave rovibronic spectrum involving levels within ϳ10 cm Ϫ1 of the first dissociation limit. The Ne 2 ϩ ions are both vibrationally and rotationally hot: the spectrum involves levels up to at least Jϭ25/2 and there is evidence for transitions involving levels near the second dissociation limit. The long-range levels involved have ͗r͘ up to 12 Å, compared with an equilibrium bond length of 1.756 Å for the ground electronic state. The long-range parameters of the interaction can be extracted from the fit and are compared with recent theoretical values.

The rotational spectrum of the CCP ( X Π r 2 ) radical and its C 13 isotopologues at microwave, millimeter, and submillimeter wavelengths J. Chem. Phys. 130, 014305 (2009); 10.1063/1.3043367Microwave and millimeter-wave spectroscopy of the open-shell van der Waals complex Ar -HO 2The microwave and millimeter-wave spectrum of HeH 2 ϩ is reported over the frequency range 6 -170 GHz. The observation of hyperfine structure in the spectra of some transitions made a clear distinction between the ortho-and para-hydrogen in the molecular ion. The hyperfine structure and double resonance Zeeman studies have enabled estimates of the quantum numbers involved in the transitions to be made. The Zeeman pattern in a 21.8 GHz doublet has been analyzed using an effective spin Hamiltonian with a case ͑B͒ basis set. This suggests an assignment of ⌬Nϭϩ1, N ϭ10←Nϭ11. A similar analysis, in an extended hyperfine basis set, for the 15.2 GHz transition suggests an assignment of either ⌬Nϭ0, Nϭ3, or Nϭ4 as appropriate assumption from which to refine the potential.

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We have used an ion beam method to observe 276 transitions in the microwave electronic spectrum of the long-range NeÉ É ÉNe`ionic complex, involving levels which lie within 10.2 cm~1 of the lowest dissociation limit. An electric Ðeld dissociation technique has been used to access directly levels with binding energies of up to 6.8 cm~1 and we have been able to construct an experimental energy level pattern for at least 17 vibrationÈrotation progressions in this region of the potential. MicrowaveÈmicrowave double resonance and Zeeman e †ect measurements have been crucial in establishing this energy level pattern. The levels are populated by the vertical electron impact ionisation of the neutral neon dimer, produced by means of a nozzle beam, with some population of higher rotational levels of the dimer ion probably resulting from larger cluster fragmentation. A case (c) e †ective Hamiltonian analysis has been successful in describing the levels in six of the progressions but a full theoretical analysis requires a coupled-states calculation. Analysis of Zeeman splittings for the microwave lines identiÐes the J values of the levels involved. The observed g-factors provide information about the transition from case (c) to case (e) coupling as both the rotational quantum number increases and the energy levels become more weakly bound.