Dissociation dynamics of higher-order He2···I35Cl(B,v′=3) complexes

Quantum effects on the stability of the He5 I2 van der Waals conformers

We present 15-dimensional quantum multiconfiguration time-dependent Hartree calculations of the vibrational levels of the He₅ I₂ van der Waals (vdW) complex employing an ab initio-based potential energy surface (PES). The energies and spatial features of such bound structures are analyzed, providing predictions on the structures and relative stabilities of its three lowest isomers. We found that the most stable isomer corresponds to all five He atoms encircling the I₂ molecule, indicating that in this case the anharmonic quantum effects do not stabilize the isomers involving a He atom in a linear configuration as reported previously for the smaller He_N I₂ systems. Such finding provides information on the overall structuring of the finite-size-solvent systems, highlighting the intriguing interplay between weak intermolecular interactions and quantum effects. © 2019 Wiley Periodicals, Inc.

Preferential stabilization of HeI2 van der Waals isomers: the effect of energetics and temperature

Energetics and temperature dependence on the preferential stabilization of the linear/T-shaped HeI₂ isomers.

Vibrational Calculations of Higher-Order Weakly Bound Complexes: The He3,4I2 Cases

The structure and relative stability of higher-order He3,4I2 clusters are investigated by carrying out full-dimensional quantum calculations within the multiconfiguration time-dependent Hartree framework. The full interaction between the I2 molecule and the He atoms is based on analytical three-body ab initio He-I2 potentials obtained from high level ab initio calculations plus the He-He interaction. The low-lying minima on the potential surfaces are found to be very close in energy with the He atoms in a ring encircling the dopant for the global minimum structure, while for the local minima one or two of the He atoms prefer the linear arrangements along the I2-axis. Such classical description on the basis of the potential energy landscape is corrected by including anharmonic quantum effects, present in highly floppy systems, by carrying out full dimensional quantum calculations. The potential energy operator was constructed by natural potential fits, while a mode combination scheme was employed to optimize the computational cost of the improved relaxation calculations. The obtained results predict the relative stability of the He3,4I2 isomers at zero temperature and provide benchmark data on binding energies and structural properties of these van der Waals systems. The (2,1) and (2,2), involving two He atoms in the T-shape and one or two He atoms in the linear configurations, respectively, are found to be the most stable isomers, although extremely close in energy with the (3,0) and (4,0) ones as predicted by classical optimizations. Comparison with experimental data on similar systems at low temperatures is also discussed. This analysis indicates once more the importance of quantum delocalization and the need of accurate quantum-mechanical treatments to characterize such doped helium nanosystems.

Effect of the intermolecular excitation in the vibrational predissociation dynamics of van der Waals complexes and the implications for control

The effect of intermolecular excitation on the vibrational predissociation lifetime is investigated systematically for different vdW complexes Rg-X2(B, v') (Rg = rare gas atom, X = halogen atom) by means of wave packet simulations. The lifetime as a function of intermolecular excitation displays a pattern of maxima and minima, with a similar shape for the different Rg-X2(B, v') complexes. The pattern is consistent with previous experimental findings involving lifetimes of intermolecular excitations in similar systems. The structure of the lifetime pattern is found to be determined by the shape of the resonance wave functions in the two van der Waals degrees of freedom, and more specifically by the magnitude of the overlap between the wave function and the coupling responsible for predissociation. Lifetime maxima and minima are associated with minima and maxima of this overlap, respectively. Implications for control of the complex lifetime are discussed.