Bound states of the OH(2Π)–HCl complex on ab initio diabatic potentials

Groenenboom, Gerrit C.; Fishchuk, Anna V.; van der Avoird, Ad

doi:doi:10.1063/1.3123426

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Infrared multiphoton electron detachment spectroscopy of C762−

In this letter, we report the first infrared spectrum of C762−. This multiply charged anion has been studied in an electrodynamic ion trap held at room temperature using tunable infrared radiation from a free-electron laser. Resonant vibrational excitation is found to cause electron detachment and the resulting singly negatively charged as well as the remaining doubly charged parent ion are monitored as a function of IR wavelength in an experimental scheme that we term infrared multiphoton elec...

Ab initio study of the spectroscopy of AgBr: A CASSCF+Averaged Coupled Pair Functional approach to the lowest excited states including spin-orbit couplings

The nine lowest-lying singlet and triplet (X 1Σ+, 2 1Σ+, 3 1Σ+, 3Σ+, 1 3,1Π, 2 3Π, and 3,1Δ) electronic states of AgBr were studied through state-specific Complete Active Space Self-Consistent Field with 16 active electrons in 12 orbitals followed by extensive Averaged Coupled Pair Functional and CIPT2 calculations with large optimized valence basis sets. The spin-orbit effects were included to obtain the Ω fine-structure states arising from the |ΛSΣ〉 parents. Even before the inclusion of the s...

The bound states of the open-shell OH(²Π)–HCl complex were calculated in four dimensions with a diabatic model using electronic states that correlate asymptotically with the ground and excited spin-orbit states of the OH(²Π) fragment and the ground state of the HCl fragment. The ab initio diabatic potentials and their analytic expansion applied in these calculations were obtained earlier by Wormer et al. [J. Chem. Phys. 122, 244325 (2005)] . In addition to the four-dimensional calculations, we considered a (3+1)-dimensional model in which the intermolecular distance coordinate R is adiabatically separated from the remaining coordinates. Both models include the important spin-orbit coupling in the OH fragment. Energy levels and parity splittings were computed for a total angular momentum of J = ½ and math

; rotational constants and other spectroscopic parameters were extracted from these calculations. The vibrationally averaged geometry in the ground state of the complex is planar and this state is more or less localized near the minimum in the lowest adiabatic potential with binding energy D_e = 1123 cm⁻¹; the dissociation energy D₀ with respect to OH(²Π_3/2) and HCl is found to be 685 cm⁻¹. The splitting between the ²Π_3/2 and ²Π_1/2 spin-orbit states of free OH is largely reduced by the anisotropic interaction with HCl through the off-diagonal diabatic coupling potential and these states are strongly mixed. Low lying rovibronic states that correlate with the OH(²Π_3/2) ground state were found at 14 cm⁻¹ for total angular momentum projection quantum number |Ω| = math

and 26 cm⁻¹ for |Ω| = ½, relative to the ground state with |Ω| = ½. The OH–HCl stretch fundamental frequency equals to 93.6 cm⁻¹, the lowest bend excited states (involving a coupled bend motion of both fragments) were found in the region of 150–160 cm⁻¹ above the ground state. Especially in the excited states important nonadiabatic effects are observed that involve both of the asymptotically degenerate adiabatic electronic states. In some of these excited states the vibrationally averaged geometry is nonplanar.

Article Outline

INTRODUCTION
THEORY
BOUND STATE CALCULATIONS
1. 4D calculations
2. (3+1)D calculations
RESULTS AND DISCUSSION
1. Assignment of bound states
2. Interpretation and discussion
SUMMARY AND CONCLUSIONS

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KEYWORDS and PACS

Keywords

ab initio calculations, binding energy, bound states, dissociation energies, excited states, ground states, hydrogen compounds, oxygen compounds, rotational states, rotational-vibrational states, spin-orbit interactions

PACS

33.20.Vq

Vibration-rotation analysis
33.20.Wr

Vibronic, rovibronic, and rotation-electron-spin interactions
31.15.aj

Relativistic corrections, spin-orbit effects, fine structure; hyperfine structure
33.15.Ry

Ionization potentials, electron affinities, molecular core binding energy
33.20.Sn

Rotational analysis

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.3123426

PUBLICATION DATA

ISSN

0021-9606 (print)

1089-7690 (online)

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American Institute of Physics

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