Ab initio model for the chlorophyll-lutein exciton coupling in the LHCII complex

Khokhlov, Daniil; Belov, A.I.

doi:10.1016/j.bpc.2019.01.001

Cited by 20 publications

(32 citation statements)

References 40 publications

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“…This implies that the mass distributions shown in Figure 2 would, on average, undergo a horizontal shift toward shorter ignition times as self-heating continues to increase the background temperature. This is qualitatively consistent with the predicted by Khokhlov evolution of ignition times (see Section 3.4 and Figure 6 in Khokhlov 1991b).…”

Section: Relation To the Khokhlov's Semi-analytic Detonation Modelsupporting

confidence: 92%

“…The fact that no detonations are observed in carbon-oxygen boundary layers of systems with a total mass below 2.1 M can then be explained by mesh resolution inadequate to resolve turbulence in simulations of merging white dwarfs binaries. Khokhlov (1991b) considered a scenario in which a detonation is created in the process of gradual strengthening of pre-existing flow perturbations by plasma self-heating due to thermonuclear burning. Because realistic multidimensional simulations were not computationally feasible at the time of his study, Khokhlov adapted a statistical formulation of Meyer & Oppenheim (1971) to describe distribution of plasma temperature fluctuations, or ignition times, on small scales.…”

Section: Numerical Effectsmentioning

confidence: 99%

“…This mechanism has been considered as a particular source of DDT in the single-degenerate scenario (Khokhlov et al 1997;Woosley et al 2011a, and references therein). In the case that the medium is inhomogeneous, the detonation may emerge as the result of a sequence of discrete ignition events, as described in the SWACER mechanism (Khokhlov 1991b;Oran & Gamezo 2007). More recently, based on the results of direct numerical simulations of turbulent chemical combustion, it has been suggest that a special preconditioning of the medium may not be required for DDT to occur (Poludnenko et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Detonability of white dwarf plasma: turbulence models at low densities

Fenn¹,

Plewa²

2017

Monthly Notices of the Royal Astronomical Society

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We study the conditions required to produce self-sustained detonations in turbulent, carbon-oxygen degenerate plasma at low densities. We perform a series of threedimensional hydrodynamic simulations of turbulence driven with various degrees of compressibility. The average conditions in the simulations are representative of models of merging binary white dwarfs. We find that material with very short ignition times is abundant in the case that turbulence is driven compressively. This material forms contiguous structures that persist over many ignition times, and that we identify as prospective detonation kernels. Detailed analysis of prospective kernels reveals that these objects are centrally-condensed and their shape is characterized by low curvature, supportive of self-sustained detonations. The key characteristic of the newly proposed detonation mechanism is thus high degree of compressibility of turbulent drive. The simulated detonation kernels have sizes notably smaller than the spatial resolution of any white dwarf merger simulation performed to date. The resolution required to resolve kernels is 0.1 km. Our results indicate a high probability of detonations in such well-resolved simulations of carbon-oxygen white dwarf mergers. These simulations will likely produce detonations in systems of lower total mass, thus broadening the population of white dwarf binaries capable of producing Type Ia supernovae. Consequently, we expect a downward revision of the lower limit of the total merger mass that is capable of producing a prompt detonation. We review application of the new detonation mechanism to various explosion scenarios of single, Chandrasekhar-mass white dwarfs.

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Section: Relation To the Khokhlov's Semi-analytic Detonation Modelsupporting

confidence: 92%

Section: Numerical Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detonability of white dwarf plasma: turbulence models at low densities

Fenn¹,

Plewa²

2017

Monthly Notices of the Royal Astronomical Society

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“…In the frame of single-degenerate (SD) explosion scenarios, the formation of a (partially) layered ejecta structure can be explained with a mechanism in which the deflagration turns into detonation, due to a the deflagrationto-detonation transition (DDT, Khokhlov 1991a). In classical DDT models, the WD becomes unbound during the deflagration phase; in a variation, the pulsational delayed detonation (PDD) models, the WD remains bound at the end of the deflagration phase, then undergoes a pulsation followed by a delayed detonation (Ivanova et al 1974;Khokhlov 1991b;Höflich, Khokhlov & Wheeler 1995). Based on other assumptions, detonation can happen via a sudden energy release in a confined fluid volume; this group of models includes gravitationally confined detonations (GCD, see e.g.…”

Section: Introductionmentioning

confidence: 99%

Abundance tomography of Type Iax SN 2011ay with tardis

Barna

Szalai

Kromer

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed spectral analysis of Type Iax SN 2011ay. Our spectra cover epochs between -3 and +19 days with respect to the maximum light in B-band. This time range allows us to employ a so-called abundance tomography technique. The synthetic spectral fitting was made with the 1D Monte Carlo radiative transfer code TARDIS. In this paper, we describe our method to fit multiple epochs with a self-consistent, stratified atmospheric model. We compare our results to previously published SYN++ models and the predictions of different explosion scenarios. Using a fixed density profile (exponential fit of W7), we find that a uniform abundance model cannot reproduce the spectral features before maximum light because of the emergence of excessively strong Fe lines. In our best-fit TARDIS model, we find an abundance profile that separated into two different regimes: a well-mixed region under 10,000 km s −1 and a stratified region with decreasing IGE abundances above 10,000 km s −1 . Based on a detailed comparative analysis, our conclusion is that the available pure deflagration models cannot fully explain either the observed properties of SN 2011ay or the results of our TARDIS modeling. Further examinations are necessary to find an adequate explanation for the origin of this object.

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“…With regard to J our earlier semi-empirical models of LHCII estimated this to be 10−20 cm −1 (Chmeliov et al 2015;Fox et al 2017) and a more recent, high-level, calculation has placed it at 21.9 cm −1 (Khokhlov and Belov 2019). One problem is that S 1 is rigorously optically-forbidden, which means that these calculations cannot be corrected against spectroscopic data and are therefore open to the intrinsic numerical errors of quantum chemistry.…”

Section: Contribution Of Excitonic Quenching To the Npq Mechanismmentioning

confidence: 99%

Excitation quenching in chlorophyll–carotenoid antenna systems: ‘coherent’ or ‘incoherent’

Balevičius

Duffy

2020

Photosynth Res

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Plants possess an essential ability to rapidly down-regulate light-harvesting in response to high light. This photoprotective process involves the formation of energy-quenching interactions between the chlorophyll and carotenoid pigments within the antenna of Photosystem II (PSII). The nature of these interactions is currently debated, with, among others, 'incoherent' or 'coherent' quenching models (or a combination of the two) suggested by a range of time-resolved spectroscopic measurements. In 'incoherent quenching', energy is transferred from a chlorophyll to a carotenoid and is dissipated due to the intrinsically short excitation lifetime of the latter. 'Coherent quenching' would arise from the quantum mechanical mixing of chlorophyll and carotenoid excited state properties, leading to a reduction in chlorophyll excitation lifetime. The key parameters are the energy gap, Δ = Car − Chl , and the resonance coupling, J, between the two excited states. Coherent quenching will be the dominant process when −J < Δ < J, i.e., when the two molecules are resonant, while the quenching will be largely incoherent when Chl > ( Car + J). One would expect quenching to be energetically unfavorable for Chl < ( Car − J). The actual dynamics of quenching lie somewhere between these limiting regimes and have non-trivial dependencies of both J and Δ . Using the Hierarchical Equation of Motion (HEOM) formalism we present a detailed theoretical examination of these excitation dynamics and their dependence on slow variations in J and Δ . We first consider an isolated chlorophyllcarotenoid dimer before embedding it within a PSII antenna sub-unit (LHCII). We show that neither energy transfer, nor the mixing of excited state lifetimes represent unique or necessary pathways for quenching and in fact discussing them as distinct quenching mechanisms is misleading. However, we do show that quenching cannot be switched 'on' and 'off' by fine tuning of Δ around the resonance point, Δ = 0. Due to the large reorganization energy of the carotenoid excited state, we find that the presence (or absence) of coherent interactions have almost no impact of the dynamics of quenching. Counterintuitively significant quenching is present even when the carotenoid excited state lies above that of the chlorophyll. We also show that, above a rather small threshold value of J > 10 cm −1 quenching becomes less and less sensitive to J (since in the window −J < Δ < J the overall lifetime is independent of it). The requirement for quenching appear to be only that J > 0. Although the coherent/incoherent character of the quenching can vary, the overall kinetics are likely robust with respect to fluctuations in J and Δ . This may be the basis for previous observations of NPQ with both coherent and incoherent features. energy gap, Δ , and resonance coupling, J. The solid lines are contours indicating points where the lifetime of the state is the same. e The same for the short-lived Car-like state ( |ex2 >). f, g are a clearer representation of the data in (d, e) for re...

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Ab initio model for the chlorophyll-lutein exciton coupling in the LHCII complex

Cited by 20 publications

References 40 publications

Detonability of white dwarf plasma: turbulence models at low densities

Detonability of white dwarf plasma: turbulence models at low densities

Abundance tomography of Type Iax SN 2011ay with tardis

Excitation quenching in chlorophyll–carotenoid antenna systems: ‘coherent’ or ‘incoherent’

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