On the spin-orbit splitting of the rare gas-monohalide molecular ground state

High-quality, ab initio potential energy functions are obtained for the interaction of bromine atoms and anions with atoms of the six rare gases (Rg) from He to Rn. The potentials of the nonrelativistic (2)Sigma(+) and (2)Pi electronic states arising from the ground-state Br((2)P)-Rg interactions are computed over a wide range of internuclear separations using a spin-restricted version of the coupled cluster method with single and double excitations and noniterative correction to triple excitations [RCCSD(T)] with an extrapolation to the complete basis set limit, from basis sets of d-aug-cc-pVQZ and d-aug-cc-pV5Z quality. These are compared with potentials derived previously from experimental measurements and ab initio calculations. The same approach is used also to refine the potentials of the Br(-)-Rg anions obtained previously [Buchachenko et al., J. Chem. Phys. 125, 064305 (2006)]. Spin-orbit coupling in the neutral species is included both ab initio and via an atomic approximation; deviations between two approaches that are large enough to affect the results significantly are observed only in the Br-Xe and Br-Rn systems. The resulting relativistic potentials are used to compute anion zero electron kinetic energy photoelectron spectra, differential scattering cross sections, and the transport coefficients of trace amounts of both anionic and neutral bromine in the rare gases. Comparison with available experimental data for all systems considered proves a very high precision of the present potentials.

Section: Ab Initio Methodsmentioning

confidence: 99%

Interactions between anionic and neutral bromine and rare gas atoms

Buchachenko

Grinev²,

Wright³

et al. 2008

“…In the current study it was found necessary to adjust the repulsive wall of one of the neutral diatomic potentials to fulfill this requirement because at very short range the original XeI X, I, and II state potentials yield an iodine spin-orbit coupling constant ⌬ so ͑I͒ slightly smaller than in atomic iodine. [60][61][62] This was achieved by slightly increasing the ␤ 1 parameter for the II state potentials in both potential parameter sets. The values obtained this way are given in parentheses in Table II.…”

Section: A Two-body Potential Functionsmentioning

confidence: 99%

Zero electron kinetic energy and threshold photodetachment spectroscopy of XenI− clusters (n=2–14): Binding, many-body effects, and structures

Lenzer

Furlanetto

Pivonka

et al. 1999

Origins and modeling of many-body exchange effects in van der Waals clustersXe n I Ϫ van der Waals clusters have been investigated by anion zero electron kinetic energy ͑ZEKE͒ and partially discriminated threshold photodetachment ͑PDTP͒ spectroscopy. The experiments yield size-dependent electron affinities ͑EAs͒ and electronic state splittings between the X, I, and II states accessed by photodetachment. Cluster minimum energy structures have been determined by extensive simulated annealing molecular dynamics calculations using Xe-I ͑Ϫ͒ pair potentials from anion ZEKE spectroscopy and various nonadditive terms. The EAs calculated without many-body effects overestimate the experimental EAs by up to 3000 cm Ϫ1 . Repulsive many-body induction in the anion clusters is found to be the dominant nonadditive effect, though the attractive interaction between the iodide charge and the Xe 2 exchange quadrupole is also important. Unique global minimum energy structures for the anion clusters arise from the influence of the many-body terms, yielding, e.g., arrangements with a closed shell of xenon atoms around the iodide anion for the clusters with nϭ12-14. The specific dependence of the EA curve on cluster size allows us to refine the absolute Xe-I bond lengths for the anion, X, I, and II state diatomic potentials to within Ϯ0.05 Å.

“…33͒ is comparable in magnitude to the interaction energy of the Na +¯I• complex. 35 In order to include spin-orbit effects in our ab initio calculations, we employed the effective one-electron spinorbit operator from the relativistic pseudopotential for the iodine atom by Peterson and co-workers. In the field of the sodium cation, the zero-field SO levels of I • give rise to three spin-orbit states: one with ⍀ =3/2 and two with ⍀ =1/2 ͑cf.…”

Section: Spin-orbit Potential Curvesmentioning

confidence: 99%

“…4,5,34,35,38,39 The full Hamiltonian including SO coupling for a particular Na-I distance r can thus be expressed in terms of the 2 ⌸ and 2 ⌺ ⌳− S states derived from ab initio calculations, and the spin-orbit coupling constant as 5,34 Ĥ ͑r͒ = ΄ 2 ⌺͑r͒ 2 ⌸͑r͒ 2 ⌸͑r͒ ΅ . Consequently, it is possible to treat spin-orbit interactions via a semiempirical approach and avoid ab initio calculations of the SO matrix elements.…”

Section: Spin-orbit Potential Curvesmentioning

confidence: 99%

See 1 more Smart Citation

Accurate ab initio potential for the Na+⋯I• complex

Timerghazin

Koch

Peslherbe

2006

High-level ab initio calculations employing the multireference configuration interaction and coupled clusters methods with a correlation-consistent sequence of basis sets have been used to obtain accurate potential energy curves for the complex of the sodium cation with the iodine atom. Potential curves for the first two electronic Lambda-S states have very different characters: the potential for the 2pi state has a well depth of approximately 10 kcal/mol, while the 2sigma state is essentially unbound. This difference is rationalized in terms of the anisotropic interaction of the quadrupole moment of the iodine atom with the sodium cation, which is stabilizing in the case of the 2pi state and destabilizing in the case of the 2sigma state. The effects of spin-orbit coupling have been accounted for with both ab initio and semiempirical approaches, which have been found to give practically the same results. Inclusion of spin-orbit interactions does not affect the X(omega = 32) ground state, which retains its 2pi character, but it results in two omega = 12 spin-orbit states, with mixed 2sigma and 2pi characters and binding energies roughly half of that of the ground spin-orbit state. Complete basis set (CBS) extrapolations of potential curves, binding energies, and equilibrium geometries were also performed, and used to calculate a number of rovibronic parameters for the Na+...I* complex and to parameterize model potentials. The final CBS-extrapolated and zero-point vibrational energy-corrected binding energy is 10.2 kcal/mol. Applications of the present results for simulations of NaI photodissociation femtosecond spectroscopy are discussed.