A Method of Diatomics in Molecules. III. H 2 X and X 2 H (X = H, F, Cl, Br, and I)

129

113

In this paper we investigate the B state predissociation and subsequent geminate recombination of photoexcited iodine in liquid xenon using a coupled quantum-classical molecular dynamics method and a model Hamiltonian gained from the diatomics-in-molecules semiempirical approach to excited state electronic structure including spin-orbit coupling. We explore the capabilities of these techniques as applied to studying the dynamics of realistic condensed phase reactions by comparing with available experimental data from recent ultrafast spectroscopic studies and Raman scattering measurements. We present a microscopic understanding of how the solvent perturbs the electronic states of the chromophore and opens various channels for dissociation from the bound excited B state. We survey the different possible dissociative channels and determine their relative importance as a function of solvent density. We find that predissociation usually occurs during the first bond extension within about 50-100 fs. We follow our trajectories out to 2 ps and observe early solvent collisions which, at the highest solvent densities studied, often result in geminate recombination to the excited bound AЈ state with in this time.

Section: A Dim Methodsmentioning

confidence: 99%

Nonadiabatic molecular dynamics simulation of photodissociation and geminate recombination of I2 liquid xenon

Batista¹,

Coker²

1996

129

113

“…In this section we present our implementation of the diatomics-in-ionic systems method ͑DIIS͒ for computing potential energy surfaces ͑PES͒ of covalent and electron transfer ion pair molecular states of an I 2 molecule embedded in solid argon. This semiempirical approach is the diatomics-inmolecules ͑DIM͒ method [50][51][52] supplemented by classical expressions for the induction energy and has been successfully investigated by Last et al 34 in studies of chlorine atoms embedded in xenon clusters.…”

Section: Diatomics-in-ionic-systems Calculation Of Ion Pair Statesmentioning

confidence: 99%

Nonadiabatic molecular dynamics simulation of ultrafast pump-probe experiments on I2 in solid rare gases

Batista

Coker

1997

113

103

Recent experimental studies of both A and B state photoexcitation of I 2 and the ensuing many-body dynamics in rare gas matrices by Apkarian and co-workers are simulated using the methods we presented in an earlier work combining nonadiabatic molecular dynamics with semiempirical diatomics-in-molecules ͑DIM͒ excited state electronic structure techniques. We extend our DIM methods to compute the ion pair states of the I 2-rare gas crystal system and use these states together with a model of the configurational dependence of the electronic dipole operator matrix elements to calculate the time resolved probe absorption signals in these pump-probe experiments using a simple golden rule result. Our computed signals are in remarkable agreement with experiments and we use our calculations to provide a detailed microscopic analysis of the channels to predissociation and recombination underlying these experiments.

“…These methods are either based on an excited state generalization of the distributed multipole approach of Stone, 7-12 or on a semiempirical valence bondlike approach known as diatomics in molecules ͑DIM͒ originally proposed by Ellison. 1,[13][14][15][16][17][18][19][20][21][22][23][24] These methods attempt to explicitly incorporate the influence of solvent on the chromophore electronic states. The second area of recent theoretical and computational development which has been crucial for the detailed microscopic modeling of these sorts of electronic relaxation processes has been the formulation of semiclassical methods for handling the mixing of electronic states [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] which occurs due to the time dependence of the quantum electronic Hamiltonian as a result of the assumed classical motion of the heavy nuclei.…”

Section: Introductionmentioning

confidence: 99%

“…-"CO 2 … n We employ the diatomics in ionic systems ͑DIIS͒ [16][17][18]69 method, a valence-bondlike approach based on the diatomics in molecules ͑DIM͒ method, [13][14][15] to obtain the excited electronic states of our molecular cluster anion system. Our implementation is designed specifically to treat the situation of strong spin-orbit coupling, typical of iodine, and the basis set we employ uses p-functions to explicitly incorporate the anisotropic interactions of the open shell I• radical when the molecular anion dissociates.…”

mentioning

confidence: 99%

Nonadiabatic molecular dynamics simulations of the photofragmentation and geminate recombination dynamics in size-selected I2−⋅(CO2)n cluster ions

Margulis¹,

Coker²

1999

Erratum: "On nonadiabatic molecular dynamics simulations of the photofragmentation and geminate recombination dynamics in size-selected I 2 − Ar n cluster ions" [J.Nonadiabatic molecular dynamics simulations of the photofragmentation and geminate recombination dynamics in size-selected I 2 − Ar n cluster ionsIn this paper we investigate the photodissociation, geminate recombination and relaxation dynamics in size-selected I 2 Ϫ •(CO 2 ) n cluster ions using an electronically nonadiabatic molecular dynamics method and a model Hamiltonian gained from diatomics-in-ionic systems ͑DIIS͒. These theoretical studies make contact with recent time resolved pump-probe and photoelectron detachment experiments. Our studies reveal a rich excited state dynamics in which various competing electronic relaxation channels as well as vibrational relaxation influence the recovery of signal in these experiments.