Microwave and millimeter-wave spectrum of the He⋯H2+ long-range complex

Abstract

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.

Near dissociation states for H2+–He on MRCI and FCI potential energy surfaces

“…The 15.2 GHz transition was assigned to a low-N transition (in the terminology of Ref. 12 , N is the spin-free angular momentum which is J in the present work) with ∆N = 0 with N = 3 or N = 4 in ortho-H + 2 -He. In the following, N is used when referring to the analysis of the experiments 12 whereas J is used when discussing the present calculations.…”

“…A tentative assignment in particular for the 15.2 GHz and 21.8 GHz transitions has been given previously based on experiments using electric field dissociation. 12 They were analyzed using an effective Hamiltonian. The 15.2 GHz transition was assigned to a low-N transition (in the terminology of Ref.…”

“…Furthermore, several long-range states for H + 2 -He have been characterized from microwave spectroscopy and by using electric field extraction. 11,12 However, the interpretation of these spectra has remained elusive, in part due to the limited accuracy of the available potential energy surfaces.…”

Improving potential energy surfaces using measured Feshbach resonance states

“…Next, morphing was applied to all three PESs, including the FCI PES. The FCI PES has been validated with respect to experiment (22)(23)(24)26) and therefore can serve as a suitable proxy for changes required for PESs at the MRCI + Q and MP2 levels of theory. Two morphing strategies were considered (Fig.…”

Rotational action spectroscopy of trapped molecular ions

“…The latter three complexes are interesting, as they are floppy, consist of only hydrogen and helium atoms, and are thus fundamental few-electron systems. For H 2 -He, although being a fundamental three-electron system, only difficult-to-assign microwave spectra close to the dissociation limit exist 118,119 , as well as ab initio data for its rovibrational levels 115,116,120 . This ion may have played an important role in the early universe, and it still plays an important role in astrochemistry as the intermediate collision complex in the fundamental He − H + 2 scattering process.…”