The future of chemical physics

Zewail, Ahmed H.

doi:10.1016/j.chemphys.2010.09.008

Cited by 4 publications

(6 citation statements)

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“…4 shows the Pmod DCS for θ R ≤ 40 • when just the leading n = 0 pole, J 0 = 16.407 + 0.886i, is retained in the pole sums of Eq. (17). Again the position and period of the oscillations is approximately reproduced, which implies that a single Regge pole, J 0 , is an important contributor to the small-angle scattering.…”

Section: Resultsmentioning

confidence: 68%

Resonance Regge poles and the state-to-state F + H2 reaction: QP decomposition, parametrized S matrix, and semiclassical complex angular momentum analysis of the angular scattering

Connor

2013

The Journal of Chemical Physics

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Three new contributions to the complex angular momentum (CAM) theory of differential cross sections (DCSs) for chemical reactions are reported. They exploit recent advances in the Padé reconstruction of a scattering (S) matrix in a region surrounding the ReJ axis, where J is the total angular momentum quantum variable, starting from the discrete values, J = 0, 1, 2, .... In particular, use is made of Padé continuations obtained by Sokolovski, Castillo, and Tully [Chem. Phys. Lett. 313, 225 (1999)] for the S matrix of the benchmark F + H2(v(i) = 0, j(i) = 0, m(i) = 0) → FH(v(f) = 3, j(f) = 3, m(f) = 0) + H reaction. Here v(i), j(i), m(i) and v(f), j(f), m(f) are the initial and final vibrational, rotational, and helicity quantum numbers, respectively. The three contributions are: (1) A new exact decomposition of the partial wave (PW) S matrix is introduced, which is called the QP decomposition. The P part contains information on the Regge poles. The Q part is then constructed exactly by subtracting a rapidly oscillating phase and the PW P matrix from the input PW S matrix. After a simple modification, it is found that the corresponding scattering subamplitudes provide insight into the angular-scattering dynamics using simple partial wave series (PWS) computations. It is shown that the leading n = 0 Regge pole contributes to the small-angle scattering in the centre-of-mass frame. (2) The Q matrix part of the QP decomposition has simpler properties than the input S matrix. This fact is exploited to deduce a parametrized (analytic) formula for the PW S matrix in which all terms have a direct physical interpretation. This is a long sort-after goal in reaction dynamics, and in particular for the state-to-state F + H2 reaction. (3) The first definitive test is reported for the accuracy of a uniform semiclassical (asymptotic) CAM theory for a DCS based on the Watson transformation. The parametrized S matrix obtained in contribution (2) is used in both the PW and semiclassical parts of the calculation. Powerful uniform asymptotic approximations are employed for the background integral; they allow for the proximity of a Regge pole and a saddle point. The CAM DCS agrees well with the PWS DCS, across the whole angular range, except close to the forward and backward directions, where, as expected, the CAM theory becomes non-uniform. At small angles, θ(R) ≲ 40°, the PWS DCS can be reproduced using a nearside semiclassical subamplitude, which allows for a pole being close to a saddle point, plus the farside surface wave of the n = 0 pole sub-subamplitude, with the oscillations in the DCS arising from nearside-farside interference. This proves that the n = 0 Regge resonance pole contributes to the small-angle scattering.

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Section: Resultsmentioning

confidence: 68%

Resonance Regge poles and the state-to-state F + H2 reaction: QP decomposition, parametrized S matrix, and semiclassical complex angular momentum analysis of the angular scattering

Connor

2013

The Journal of Chemical Physics

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“…Where there is data we also find . Therefore, a proper theoretical understanding of these complexes should be able to describe these common properties and the clear differences among the complexes on the basis of simple chemical and physical understanding as well as via detailed computation [61].…”

Section: Discussionmentioning

confidence: 99%

“…In his wonderful article "The future of chemical physics", Ahmed Zewail [61] wrote that "Breakthroughs will continue to emerge when … pertinent concepts are generalized with the help of "simple, but not too simple" theories. Computations should be considered as tools, keeping in mind that large-scale computations without a "final" theoretical condensate (or better yet, a "simple equation") are like large-scale experiments which produce numerous results that do not boil down to a meaningful finding.…”

Section: Introductionmentioning

confidence: 99%

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Theories of phosphorescence in organo-transition metal complexes – From relativistic effects to simple models and design principles for organic light-emitting diodes

Powell

2015

Coordination Chemistry Reviews

111

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We review theories of phosphorescence in cyclometalated complexes. We focus primarily on pseudooctahedrally coordinated metals (e.g., [Os(II)(bpy)3] 2+ , Ir(III)(ppy)3 and Ir(III)(ptz)3) as, for reasons that are explored in detail, these show particularly strong phosphorescence. We discuss both first principles approaches and semi-empirical models, e.g., ligand field theory. We show that together these provide a clear understanding of the photophysics and in particular the lowest energy triplet excitation, T1. In order to build a good model relativistic effects need to be included. The role of spin-orbit coupling is well-known, but scalar relativistic effects are also large -and are therefore also introduced and discussed. No expertise in special relativity or relativistic quantum mechanics is assumed and a pedagogical introduction to these subjects is given. It is shown that, once both scalar relativistic effects and spin-orbit coupling are included, time dependent density functional theory (TDDFT) provides quantitatively accurate predictions of the radiative decay rates of the substates of T1 in phosphorescent organotranstion-metal complexes. We describe the pseudo-angular momentum model, and show that it reproduces the key experimental findings. For example, this model provides a simple explanation of the relative radiative rates of the substates of T1, which differ by orders of magnitude. Special emphasis is placed on materials with potential applications as active materials in organic light-emitting diodes (OLEDs) and principles for the design of new complexes are identified on the basis of the insights provided by the theories reviewed. We discuss the remaining theoretical challenges, which include deepening our understanding of solvent effects and, vitally, understanding and predicting nonradiative decay rates. KeywordsLigand field theory Relativistic density functional theory (DFT) Time dependent density functional theory (TDDFT) Organic light-emitting diodes (OLEDs) Ir(ppy)3 Spin-orbit coupling Scalar relativistic effects Triplet state Radiative decay rate Non-radiative decay rate Photoluminescent quantum yield (PLQY) Metal-to-ligand charge transfer (MLCT)Two major approaches have been taken to modelling the phosphorescence in organo-transition metal complexes: phenomenological or semi-empirical approaches, such as ligand field theory, and first principles approaches, primarily based on (relativistic) (time dependent) density functional theory. *

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“…[15]. Interdisplinary research around the globe is advancing, and in order to see the real Elephant [17], the story of blind men's research on an elephant in which one said this is a pillar, a second said it is a wall, and so on (Figure 1), in our research, we should 'flow' [18] with the theme of borderless science by writing, sharing, and discussing with one another so the gap between the diverse scientific communities can be closed.…”

mentioning

confidence: 99%

Creating a Borderless Platform for Scientific Research in Canadian Chemical Transactions

Halim

Sarwar²,

Hosein³

et al. 2013

Can Chem Trans

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The future of chemical physics

Cited by 4 publications

References 5 publications

Resonance Regge poles and the state-to-state F + H2 reaction: QP decomposition, parametrized S matrix, and semiclassical complex angular momentum analysis of the angular scattering

Resonance Regge poles and the state-to-state F + H2 reaction: QP decomposition, parametrized S matrix, and semiclassical complex angular momentum analysis of the angular scattering

Theories of phosphorescence in organo-transition metal complexes – From relativistic effects to simple models and design principles for organic light-emitting diodes

Creating a Borderless Platform for Scientific Research in Canadian Chemical Transactions

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