Semiclassical Initial Value Representation Method Research Articles

A direct approach to one photon interference contributions in the coherent control of photodissociation

Formally exact quantum mechanical expressions for cumulative transition matrix elements μjk(ξ,E)=∑n〈j|με|E,ξ,n−〉〈E,ξ,n−|με|k〉, central to one photon coherent control scenarios of photodissociation, are derived. The resultant approach bypasses the need for solving the complete state-to-state quantum mechanical reactive scattering problem to obtain control results. These exact expressions are implemented both quantum mechanically and via a semiclassical initial value representation method to investigate coherent control in the generic photodissociation of a triatomic into more than one product. The semiclassical approach is shown to provide an accurate description of bimolecular control in this system.

Semiclassical Dynamics in the Coherent Control of Nonadiabatic ICN Photodissociation

The utility of a semiclassical initial value representation (SC-IVR) to simulate coherent control is explored. Specifically, bichromatic control of the state specific ICN photodissociation in the à continuum is investigated both quantum mechanically and semiclassically, and the ability of the SC-IVR method to reproduce phases of transition matrix element products is examined. Control over the I(2P1/2)/I(2P3/2) product ratio is considerable and the resultant semiclassical photofragmentation ratios are in good agreement with full quantum dynamics calculations.

Semiclassical molecular dynamics simulations of intramolecular proton transfer in photoexcited 2-(2′-hydroxyphenyl)–oxazole

A full-dimensional excited state potential energy surface is constructed, and the proton transfer dynamics associated with the keto-enolic tautomerization reaction in photoexcited 2-(2′-hydroxyphenyl)–oxazole is simulated according to an approximate version of the semiclassical initial value representation method introduced by Miller and co-workers [V. Guallar, V. S. Batista, and W. H. Miller, J. Chem. Phys. 110, 9922 (1999)]. The full-dimensional potential energy surface is developed according to an ab initio reaction surface model obtained at the CIS level of quantum chemistry. Proton transfer is found to be substantially affected by isotopic substitution, and significantly coupled to the internal oxazole–hydroxyphenyl in-the-plane bending mode. The nascent tautomer is found to be stabilized primarily through vibrational energy redistribution into all of the remaining in-the-plane vibrational modes. The accuracy of the methodology is verified by reducing the dimensionality of the system and comparing our semiclassical results with full quantum mechanical calculations.

Nonadiabatic photodissociation dynamics of ICN in the à continuum: A semiclassical initial value representation study

In this paper we investigate the nonadiabatic photodissociation dynamics of ICN in the à continuum, using a semiclassical initial value representation method which is able to describe electronically nonadiabatic processes through the quantization of the classical electron–nuclear model Hamiltonian of Meyer and Miller [J. Chem. Phys. 70, 3214 (1979)]. We explore the capabilities of this semiclassical technique as applied to studying the ICN absorption spectrum, and the CN rotational distribution, through direct comparison of our semiclassical results with experimental data, and with full quantum mechanical calculations. We find that the Meyer–Miller Hamiltonian, quantized according to the semiclassical prescription, describes the ICN photodissociation dynamics in excellent agreement with full-quantum mechanical calculations.

A numerical test of different integral conditioning approximations for a semiclassical initial value representation for wavepacket propagation

Recent numerical evidence indicates that the rapid spreading of nearby classical trajectories in chaotic regions results in numerical difficulties and reduced accuracy for semiclassical initial value representation methods. These problems can be significantly reduced and the accuracy of the methods increased through the application of integral conditioning techniques, which have been developed for the numerical evaluation of integrals with highly oscillatory integrands. This work studies the effectiveness of these conditioning techniques, when applied to one semiclassical initial value representation wavepacket propagation procedure, the HK propagator method.

Semiclassical molecular dynamics simulations of ultrafast photodissociation dynamics associated with the Chappuis band of ozone

In this paper we investigate the nonadiabatic ultrafast dynamics of interconversion between the two lower lying excited states of A″1 symmetry (1 A″1 and 2 A″1) of ozone following photoexcitation of the molecule in the gas phase with visible light. Our algorithm involves a semiclassical initial value representation method which is able to describe electronically nonadiabatic processes within the time dependent picture through the quantization of the classical electron–nuclear model Hamiltonian of Meyer and Miller [J. Chem. Phys. 70, 7 (1979)]. We explore the capabilities of these techniques as applied to studying the dynamics of a realistic reaction of photodissociation on full ab initio electronic potential energy surfaces. Our semiclassical results provide an intuitive understanding of the most fundamental dynamical features involved in the process of predissociation, such as decay and recurrence events, as well as an interpretation of experimental studies of the Chappuis band of ozone in the frequency domain.