Coupled-channel study of halogen (2<i>P</i>) + rare gas (1<i>S</i>) scattering

“…in which the indices 1 and 2 refer to the I atoms, is measured from the I-I axis, V ⌺ and V ⌸ are expressed as Morse functions, derived from known I-Rg potentials, 18 in which D e , r e , and ␤ are the Morse parameters, and and ⑀ are the Lennard-Jones parameters for Rg-Rg and CCl 4 -CCl 4 interactions. Note, in the form given in Eq.…”

Section: Simulationsmentioning

confidence: 99%

Predissociation dynamics of I2(B) in liquid CCl4 observed through femtosecond pump-probe measurements: Electronic caging through solvent symmetry

Zadoyan

Sterling

Ovchinnikov

et al. 1997

The Journal of Chemical Physics

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Direct observations of the solvent induced electronic predissociation of I 2 (B) in liquid CCl 4 are made using femtosecond pump-probe measurements in which fluorescence from spin-orbit excited I*I* pairs, bound by the solvent cage, is used as detection. Data is reported for initial preparations ranging from the B state potential minimum, at 640 nm, to above the dissociation limit, at 490 nm. Analysis is provided through classical simulations, to highlight the role of solvent structure on: recombination, vibrational relaxation, and decay of coherence. The data is consistent with an anisotropic I 2 (X) -CCl 4 potential which, in the first solvent shell, leads to an angular distribution peaked along the molecular axis. The roles of solvent structure and dynamics on electronic predissociation are analyzed. The data in liquid CCl 4 can be understood in terms of a curve crossing near vϭ0, at 3.05 ÅϽR c Ͻ3.8 Å, and the final surface can be narrowed down to 2 g or a(1 g ). This nonadiabatic u→g transition is driven by static and dynamic asymmetry in the solvent structure. The role of solvent structure is demonstrated by contrasting the liquid phase predissociation probabilities with those observed in solid Kr. Despite the twofold increase in density, predissociation probabilities in the solid state are an order of magnitude smaller, due mainly to the high symmetry of the solvent cage. The role of solvent dynamics is evidenced in the energy dependent measurements. Independent of the kinetic energy content in I 2 , electronic predissociation in liquid CCl 4 proceeds with a time constant equal to the molecular vibrational period. A modified Landau-Zener model, in which the effective electronic coupling is taken to be a linear function of vibrational amplitude fits the data, and suggests that cage distortions driven by the molecule enhance its predissociation probability. A nearly quantitative reproduction of the observations is possible when using the recently reported off-diagonal DIM surface that couples the B(0 u ϩ ) and a(1g) states ͓Batista and Coker, J. Chem. Phys. 105, 4033 ͑1996͔͒.

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“…We then consider a treatment in which the I 2 -Kr potentials depend on the electronic state of I 2 , by constructing the three-body potential from the anisotropic I-Kr fragments. 66,72,73 This construct is described in the Appendix, along with the justification for using isotropic pair potentials in the excited state. The need for using anisotropic potentials to describe the ground state has already been demonstrated in the analysis of the spin-orbit transition of atomic iodine isolated in solid Kr and Xe.…”

Section: Many-body Spectramentioning

confidence: 99%

“…While the experiments measure spin-orbit coupled surfaces, in a strictly lϭ1 basis set ( p x , p y , p z ), the ⌺ and ⌸ contributions can be uniquely decomposed. 73 A rather simple construct of I 2 -Kr potentials is possible in this basis set. The ground X( 1 ⌺ g ϩ ) state of I 2 arises from the overlap of p z orbitals.…”

Section: Appendixmentioning

confidence: 99%

Condensed phase spectroscopy from mixed-order semiclassical molecular dynamics: Absorption, emission, and resonant Raman spectra of I2 isolated in solid Kr

Ovchinnikov

Apkarian

1996

The Journal of Chemical Physics

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A method for spectral simulations in systems of very large dimensionality via semiclassical molecular dynamics is introduced and applied to the spectroscopy of iodine isolated in solid Kr, as a prototype of spectroscopy in condensed media in general. The method relies on constructing quantum correlation functions, C(t), using initial value propagators which correspond to the zerothand second-order approximations in stationary phase of the exact quantum propagator. The first is used for treating modes with high thermal occupation numbers, the lattice modes, while the second is used for treating the guest mode. The limits of validity of the bare propagators are tested vs exact treatments of gas phase I 2 , and shown to be quite broad. The mixed order simulations are then used to reproduce the structured A→X emission, the structureless B←X absorption, and the intensities in resonant Raman ͑RR͒ progressions of matrix isolated I 2 , connecting spectroscopic observables to molecular motions. Decompositions of the supersystem correlations into system and bath are used to provide perspectives about condensed phase spectroscopy. The system correlation can be regarded as the sampling function for the decaying bath correlation, which in turn is a summary of the many-body dynamics. The B←X absorption spectrum is determined by the coherent ballistic motion of the excited state density: Upon stretching, I 2 pushes the cage atoms out of overlap in position density, and C(t) never recovers. Due to the compressive nature of the cage coordinate in the A→X transition, C(t) decays more gently, after being sampled three times. RR spectra, which are reproduced with adiabatic dynamics, sample the complete history of the many-body correlations, however, due to the breadth in space-time of scattering into high overtones, the sampling is coarse grained. The specific dynamics that control C(t) cannot be described as dissipative.

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Coupled-channel study of halogen (2P) + rare gas (1S) scattering

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Cited by 62 publications

References 46 publications

Nonadiabatic molecular dynamics simulations of the photofragmentation and geminate recombination dynamics in size-selected I2−⋅Arn cluster ions

Nonadiabatic molecular dynamics simulations of the photofragmentation and geminate recombination dynamics in size-selected I2−⋅Arn cluster ions

Predissociation dynamics of I2(B) in liquid CCl4 observed through femtosecond pump-probe measurements: Electronic caging through solvent symmetry

Condensed phase spectroscopy from mixed-order semiclassical molecular dynamics: Absorption, emission, and resonant Raman spectra of I2 isolated in solid Kr

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