Vibrational predissociation dynamics of the He79Br2 van der Waals molecule: A quantum mechanical study

Abstract

Articles you may be interested in A full-dimensional quantum approach to the vibrational predissociation of tetra-atomic complexes based on the partially-separable time-dependent self-consistent-field approximation Oneatom cage effect in collinear I2(B)-Ar complexes: A timedependent wave packet study Validity of a hybrid quantum/classical approach in photodissociation/recombination of I2 in rare gas matrices A three-dimensional time-dependent self-consistent-field TDSCF approach is proposed to study the vibrational predissociation of the I 2 (B)-Ne van der Waals vdW complex. Jacobian coordinates are used within the assumption of zero-total angular momentum. In the method the total wave function is factorized such that the bending mode of the system is explicitly separated, while the coupling between the remaining two degrees of freedom is treated exactly. The decay dynamics of several resonances corresponding to different initial vibrational states of I 2 is investigated through long-time wave packet propagations. Calculated resonance lifetimes are compared to experimental data and found to be in quantitative agreement with them. The results show that predissociation of the complex is mainly governed by the coupling between the I 2 and the vdW stretching vibrations, whereas the bending mode has a rather weak effect on the dynamics. The good quality of the TDSCF description of this long-time dynamical process is due to the adaptation of the decoupling approximations applied in the method to the physical situation of the system. The validity of the approach is discussed in the light of the results.

An empirical potential-energy surface for the He–I2(BΠu3) van der Waals complex including three-body effects

“…In this multiexponential dynamics regime the decay curve P͑t͒ can no longer be fitted to a single exponential function. Actually, the same behavior was found in the case of He-Br 2 ͑B , Ј͒ for high Ј, 19,22 and it was attributed to possible intramolecular vibrational relaxation mechanisms. 19 With increasing Ј the width of the initial resonance state increases as well, and thus the probability of overlapping and interaction between this resonance and other Ͻ Ј resonances energetically close is expected to increase.…”

“…32͒ using a B state potential surface previously fitted through line-shape calculations assuming J =0. 19 Good agreement was found between the calculated and measured Br 2 rotational distributions. 32 The above results seem to indicate that fitting the potential parameters under the assumption of J = 0 is a reasonably good approximation.…”

“…In the case of He-Br 2 ͑B , Ј͒ a wider range of Ј levels, Ј= 8 -48, was investigated experimentally. [16][17][18] A He-Br 2 ͑B , Ј͒ empirical potential built up as an addition of pairwise interactions 19 reproduced successfully the measured spectral blueshifts and VP linewidths up to ЈӍ 38. The blueshift observed experimentally increases up to Јϳ 35, and then it decreases for higher Ј, suggesting that the vdW bond becomes stronger for high Ј levels, which correspond to large Br-Br separations ͑Ͼ4.0 Å͒.…”

Theoretical simulations of the He79Br2 B, v=8←X, v″=0 excitation spectrum: Spectroscopic manifestation of a linear isomer?

“…where the parameters R ⌳ ϭ3.81 Å and ␣ ⌳ ϭ1.55 Å Ϫ1 for both ⌳ϭ⌺,⌸ were borrowed from the X-state EMP potential, 39 while dissociation energies was taken as…”

“…agreement with experimental data on the vibrational predissociation dynamics [36][37][38] achieved even at high v's, where the intramolecular vibrational relaxation causes extreme sensitivity of the dynamics to the properties of the PESs. [39][40][41][42] We try to assign these two spectrum features to transitions from the distinct isomers having similar energies. Implementing the family of the ground-state PESs and comparing the simulated spectra with the observed one, we aim to support a new assignment which involves the coexistence of T-shaped and linear isomers and deduce the qualitative estimation of their energies which can be compared with available ab initio data.…”