The van der Waals potential energy surfaces and structures of He–ICl and Ne–ICl clusters

Stabilization and rovibronic spectra of the T -shaped and linear ground-state conformers of a weakly bound raregas-homonuclear dihalogen complex: He Br 2He 79 Br 2 B,v=8←X,v ″ =0 excitation spectrum: Ab initio prediction and spectroscopic manifestation of a linear isomer Spectroscopic features attributed to rovibronic transitions from both the T-shaped and linear He¯I 35 Cl(X) and He¯I 37 Cl(X) ground-state complexes have been recorded in the ICl B 3 ⌸ 0ϩ -X 1 ⌺ ϩ , 2-0 and 3-0 spectral regions using laser-induced fluorescence spectroscopy. Experiments performed using varying expansion conditions indicate that the He¯I 35,37 Cl(X) complex with a linear equilibrium orientation lies lower in energy than the separately localized T-shaped isomer even though the transition energies of the T-shaped and linear complexes are shifted by ϳ3.5 and ϳ14 cm Ϫ1 to higher energy than the I 35,37 Cl B -X band origins, respectively. Based on comparison with the excited state theoretical predictions of Waterland et al. ͓J. Chem. Phys. 92, 4261 ͑1990͔͒, estimates of the binding energies for the ground state T-shaped and linear He¯I 35 Cl(X) complexes are 17 and 21 cm Ϫ1 , respectively, in qualitative agreement with the recently published predictions of 15.2 and 18.3 cm Ϫ1 obtained using high level ab initio theory for the ground state potential energy surface ͓J. Chem. Phys. 117, 7017 ͑2002͔͒.

Section: Introductionmentioning

confidence: 99%

Spectroscopic observation of the preferentially stabilized, linear He⋯ICl(X 1Σ+) complex

Bradke

Loomis

2003

“…[17][18][19][20][21][22] The overall anisotropy predicted by such ab initio computations for rare gas-dihalogen systems is generally correct, although the resulting binding energies typically underestimate the experimental ones by 2-3 cm −1 . [23][24][25] Recent ab initio CCSD͑T͒ studies of the PESs of the heavy HeI 2 complex for both its ground X and excited B electronic states 26,27 show that the anisotropy in this complex is qualitatively similar to that in the lighter, e.g., HeCl 2 18 and HeBr 2 , 28,29 systems: whereas the ground state PES is characterized by two attractive wells about the linear and the perpendicular geometries, respectively, the B excited PES displays a single minimum about the T-shaped configuration. The HeI 2 ͑B͒ UCCSD͑T͒ surface 27 has been also found reasonably consistent with different empirical potentials.…”

Section: Introductionmentioning

confidence: 99%

Ab initio vibrational predissociation dynamics of He–I2(B) complex

Valdés

Prosmiti

Villarreal

et al. 2007

Self Cite

Three-dimensional quantum mechanical calculations on the vibrational predissociation dynamics of HeI 2 B state complex are performed using a potential energy surface accurately fitted to unrestricted open-shell coupled cluster ab initio data, further enabling extrapolation for large I 2 bond lengths. A Lanczos iterative method with an optimized complex absorbing potential is used to determine energies and lifetimes of the vibrationally predissociating He, I 2 ͑B , vЈ͒ complex for vЈ ഛ 26 of I 2 vibrational excitations. The calculated predissociating state energies agree with recent experimental results within 0.5 cm −1 . This excellent agreement is remarkable since no adjustment was made with respect to the experiments. The present ab initio approach, however, shows its limitations in the fact that the computed lifetimes that are highly sensitive to subtle details of the potential energy surfaces such as anisotropy, are a factor of 1.5 larger than the available experimental data.

“…topology for such systems. [17][18][19][20][21] In the light of the latest experimental data by the Loomis group, 13 we recently revisited the He-I 2 (X) vdW complex. 22 Our estimates of 15.72 cm In all these experimental studies [10][11][12][13] electronic excited states of the HeI 2 are involved, such as the B( ) states, thus for any direct comparison between theoretical simulations and experimental measurements the knowledge of the underlying intermolecular interactions is mandatory.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of the He–I2(E3Πg) ion-pair state: Ab initio intermolecular potential and vibrational levels

Καλέμος

Valdés

Prosmiti

2012

Self Cite

We present a theoretical study on the potential energy surface and vibrational bound states of the E electronic excited state of the HeI 2 van der Waals system. The interaction energies are computed using accurate ab initio methods and large basis sets. Relativistic small-core effective core potentials in conjunction with a quintuple-zeta quality basis set are employed for the heavy iodine atoms in multireference configuration interaction calculations for the 3 A and 3 A states. For the representation of the potential energy surface we used a general interpolation technique for constructing potential surfaces from ab initio data based on the reproducing kernel Hilbert space method. The surface presents global and local minima for T-shaped configurations with well-depths of 33.2 and 4.6 cm −1 , respectively. Vibrational energies and states are computed through variational quantum mechanical calculations. We found that the binding energy of the HeI 2 (E) T-shaped isomer is 16.85 cm −1 , in excellent agreement with recent experimental measurements. In lieu of more experimental data we also report our predictions on higher vibrational levels and we analyze the influence of the underlying surface on them. This is the first attempt to represent the potential surface of such a highly excited electronic state of a van der Waals complex, and it demonstrates the capability of the ab initio technology to provide accurate results for carrying out reliable studies to model experimental data.