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  1. Article ; Online: Theoretical model of femtosecond coherence spectroscopy of vibronic excitons in molecular aggregates.

    Rode, Alexander J / Arpin, Paul C / Turner, Daniel B

    The Journal of chemical physics

    2024  Volume 160, Issue 16

    Abstract: When used as pump pulses in transient absorption spectroscopy measurements, femtosecond laser pulses can produce oscillatory signals known as quantum beats. The quantum beats arise from coherent superpositions of the states of the sample and are best ... ...

    Abstract When used as pump pulses in transient absorption spectroscopy measurements, femtosecond laser pulses can produce oscillatory signals known as quantum beats. The quantum beats arise from coherent superpositions of the states of the sample and are best studied in the Fourier domain using Femtosecond Coherence Spectroscopy (FCS), which consists of one-dimensional amplitude and phase plots of a specified oscillation frequency as a function of the detection frequency. Prior works have shown ubiquitous amplitude nodes and π phase shifts in FCS from excited-state vibrational wavepackets in monomer samples. However, the FCS arising from vibronic-exciton states in molecular aggregates have not been studied theoretically. Here, we use a model of vibronic-exciton states in molecular dimers based on displaced harmonic oscillators to simulate FCS for dimers in two important cases. Simulations reveal distinct spectral signatures of excited-state vibronic-exciton coherences in molecular dimers that may be used to distinguish them from monomer vibrational coherences. A salient result is that, for certain relative orientations of the transition dipoles, the key resonance condition between the electronic coupling and the frequency of the vibrational mode may yield strong enhancement of the quantum-beat amplitude and, perhaps, also cause a significant decrease of the oscillation frequency to a value far lower than the vibrational frequency. Future studies using these results will lead to new insights into the excited-state coherences generated in photosynthetic pigment-protein complexes.
    Language English
    Publishing date 2024-04-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3113-6
    ISSN 1089-7690 ; 0021-9606
    ISSN (online) 1089-7690
    ISSN 0021-9606
    DOI 10.1063/5.0200570
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Perturbative theoretical model of electronic transient circular dichroism spectroscopy of molecular aggregates.

    Arpin, Paul C / Turner, Daniel B

    The Journal of chemical physics

    2022  Volume 157, Issue 15, Page(s) 154101

    Abstract: A chiral analog of transient absorption spectroscopy, transient circular dichroism (TCD) spectroscopy is an emerging time-resolved method. Both spectroscopic methods can probe the electronic transitions of a sample, and TCD is additionally sensitive to ... ...

    Abstract A chiral analog of transient absorption spectroscopy, transient circular dichroism (TCD) spectroscopy is an emerging time-resolved method. Both spectroscopic methods can probe the electronic transitions of a sample, and TCD is additionally sensitive to the dynamic aspects of chirality, such as those induced by molecular excitons. Here, we develop a theoretical description of TCD for electronic multi-level models in which the pump pulse is linearly polarized and probe pulse is alternately left- and right-circularly polarized. We derive effective response functions analogous to those often used to describe other four-wave mixing methods and then simulate and analyze TCD spectra for three representative multi-level electronic model systems. We elaborate on the presence and detection of the spectral signatures of electronic coherences.
    Language English
    Publishing date 2022-09-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3113-6
    ISSN 1089-7690 ; 0021-9606
    ISSN (online) 1089-7690
    ISSN 0021-9606
    DOI 10.1063/5.0119626
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Signatures of Vibrational and Electronic Quantum Beats in Femtosecond Coherence Spectra.

    Arpin, Paul C / Turner, Daniel B

    The journal of physical chemistry. A

    2021  Volume 125, Issue 12, Page(s) 2425–2435

    Abstract: Femtosecond laser pulses can produce oscillatory signals in transient-absorption spectroscopy measurements. The quantum beats are often studied using femtosecond coherence spectra (FCS), the Fourier domain amplitude, and phase profiles at individual ... ...

    Abstract Femtosecond laser pulses can produce oscillatory signals in transient-absorption spectroscopy measurements. The quantum beats are often studied using femtosecond coherence spectra (FCS), the Fourier domain amplitude, and phase profiles at individual oscillation frequencies. In principle, one can identify the mechanism that gives rise to each quantum-beat signal by comparing its measured FCS to those arising from microscopic models. To date, however, most measured FCS deviate from the ubiquitous harmonic oscillator model. Here, we expand the inventory of models to which the measured spectra can be compared. We develop quantum-mechanical models of the fundamental, overtone, and combination-band FCS arising from harmonic potentials, the FCS of anharmonic potentials, and the FCS of a purely electronic dimer. This work solidifies the use of FCS for identifying electronic coherences that can arise in measurements of molecular aggregates including photosynthetic proteins. Furthermore, future studies can use the derived expressions to fit the measured FCS and thereby extract microscopic parameters of molecular potential-energy surfaces.
    Language English
    Publishing date 2021-03-16
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5215
    ISSN (online) 1520-5215
    DOI 10.1021/acs.jpca.0c10807
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: A systematic model study quantifying how conical intersection topography modulates photochemical reactions.

    Farfan, Camille A / Turner, Daniel B

    Physical chemistry chemical physics : PCCP

    2020  Volume 22, Issue 36, Page(s) 20265–20283

    Abstract: Despite their important role in photochemistry and expected presence in most polyatomic molecules, conical intersections have been thoroughly characterized in a comparatively small number of systems. Conical intersections can confer molecular ... ...

    Abstract Despite their important role in photochemistry and expected presence in most polyatomic molecules, conical intersections have been thoroughly characterized in a comparatively small number of systems. Conical intersections can confer molecular photoreactivity or photostability, often with remarkable efficacy, due to their unique structure: at a conical intersection, the adiabatic potential energy surfaces of two or more electronic states are degenerate, enabling ultrafast decay from an excited state without radiative emission, known as nonadiabatic transfer. Furthermore, the precise conical intersection topography determines fundamental properties of photochemical processes, including excited-state decay rate, efficacy, and molecular products that are formed. However, these relationships have yet to be defined comprehensively. In this article, we use an adaptable computational model to investigate a variety of conical intersection topographies, simulate resulting nonadiabatic dynamics, and calculate key photochemical observables. We varied the vibrational mode frequencies to modify conical intersection topography systematically in four primary classes of conical intersections and quantified the resulting rate, total yield, and product yield of nonadiabatic decay. The results reveal that higher vibrational mode frequencies reduce nonadiabatic transfer, but increase the transfer rate and resulting photoproduct formation. These trends can inform progress toward experimental control of photochemical reactions or tuning of molecules' photochemical properties based on conical intersections and their topography.
    Language English
    Publishing date 2020-09-23
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/d0cp03464a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Energy transfer: Resonance is the key for coherence.

    Turner, Daniel B

    Nature chemistry

    2016  Volume 9, Issue 3, Page(s) 196–197

    Language English
    Publishing date 2016-10-31
    Publishing country England
    Document type Journal Article
    ZDB-ID 2464596-5
    ISSN 1755-4349 ; 1755-4330
    ISSN (online) 1755-4349
    ISSN 1755-4330
    DOI 10.1038/nchem.2742
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Nonadiabatic Photochemistry Induced by Inaccessible Conical Intersections.

    Farfan, Camille A / Turner, Daniel B

    The journal of physical chemistry. A

    2019  Volume 123, Issue 36, Page(s) 7768–7776

    Abstract: Conical intersections are ubiquitous in photochemical processes, where nonadiabatic transfer induces ultrafast nonradiative decay from an excited state. Although they eluded experimental detection until the 1990s, today three diagnostic attributes are ... ...

    Abstract Conical intersections are ubiquitous in photochemical processes, where nonadiabatic transfer induces ultrafast nonradiative decay from an excited state. Although they eluded experimental detection until the 1990s, today three diagnostic attributes are generally associated with photochemical reactions through conical intersections: ultrafast electronic dynamics, negligible fluorescence, and coherent wavepacket transfer. Here, we use generalized quantum dynamics simulations to show that coherent nonadiabatic transfer of excited vibrational wavepackets can occur even without reaching the conical intersection region. Instead, the wavepacket remains distant from the conical intersection throughout. In some topographies, an energetically inaccessible conical intersection can be completely avoided, yet still induce substantial nonadiabatic transfer with ultrafast transfer efficiencies that are nearly identical to those of direct transfer through a conical intersection. These results reveal that the diagnostic properties of conical intersections are not actually specific to decay pathways traveling directly through the intersection funnel, as is the common interpretation, but can also arise from alternative pathways that do not reach the intersection. This suggests that the diagnostic features and experimental signals associated with conical intersections should be reassessed, and the concept of pathways through a conical intersection as the "paradigm of photochemistry" may need to be adjusted.
    Language English
    Publishing date 2019-09-04
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5215
    ISSN (online) 1520-5215
    DOI 10.1021/acs.jpca.9b07739
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Exciton delocalization in a fully synthetic DNA-templated bacteriochlorin dimer.

    Mass, Olga A / Watt, Devan R / Patten, Lance K / Pensack, Ryan D / Lee, Jeunghoon / Turner, Daniel B / Yurke, Bernard / Knowlton, William B

    Physical chemistry chemical physics : PCCP

    2023  Volume 25, Issue 41, Page(s) 28437–28451

    Abstract: ... A ... ...

    Abstract A bacteriochlorophyll
    MeSH term(s) Light-Harvesting Protein Complexes/chemistry ; Computing Methodologies ; Quantum Theory ; Photosynthetic Reaction Center Complex Proteins/chemistry ; DNA
    Chemical Substances Light-Harvesting Protein Complexes ; bacteriochlorin ; Photosynthetic Reaction Center Complex Proteins ; DNA (9007-49-2)
    Language English
    Publishing date 2023-10-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/d3cp01634j
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Coherent Two-Quantum Two-Dimensional Electronic Spectroscopy Using Incoherent Light.

    Ulness, Darin J / Turner, Daniel B

    The journal of physical chemistry. A

    2017  

    Abstract: Two-quantum two-dimensional electronic spectroscopy (2Q 2D ES) may provide a measure of electron-correlation energies in molecules. Attempts to obtain this profound but elusive signal have relied on experimental implementations using femtosecond laser ... ...

    Abstract Two-quantum two-dimensional electronic spectroscopy (2Q 2D ES) may provide a measure of electron-correlation energies in molecules. Attempts to obtain this profound but elusive signal have relied on experimental implementations using femtosecond laser pulses, which induce an overwhelming background signal of nonresonant response. Here we explore theoretically the signatures of electron correlation in coherent 2Q 2D ES measurements that use spectrally incoherent light, I
    Language English
    Publishing date 2017-11-21
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5215
    ISSN (online) 1520-5215
    DOI 10.1021/acs.jpca.7b09443
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Coding for broader impact: leveraging coding skills for stakeholder communication

    Turner, Daniel B / Behm, Jocelyn E / Phillips, Payton M / Ramirez, Victoria A / Helmus, Matthew R

    Frontiers in ecology and the environment. 2022 May, v. 20, no. 4

    2022  

    Abstract: Sharing ecological research with stakeholders has broader impacts for conservation and sustainability outcomes. However, ecologists face major challenges to effective communication with stakeholders, including lack of reciprocal trust, unacknowledged ... ...

    Abstract Sharing ecological research with stakeholders has broader impacts for conservation and sustainability outcomes. However, ecologists face major challenges to effective communication with stakeholders, including lack of reciprocal trust, unacknowledged incentives, differing goals, and scientific inaccessibility. These obstacles largely stem from professional training in ecology prioritizing effective communication among peers over the public. Here, we argue that coding skills honed for peer communication can be leveraged to overcome these challenges within a “coding for broader impact” framework that provides tasks to promote effective communication and culminates in individualized stakeholder reports. The reports explicitly incorporate stakeholder knowledge and are coded in conjunction with tasks for peer communication. We illustrate the framework through three case studies in which we shared data and information about backyard biodiversity, agricultural impacts, and tick‐borne disease with homeowners, farmers, and land managers. A coding for broader impact framework allows a common analytical tool to become a public communication skill valuable to diverse stakeholder audiences.
    Keywords biodiversity ; environment ; stakeholders ; tick-borne diseases
    Language English
    Dates of publication 2022-05
    Size p. 255-262.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 2110853-5
    ISSN 1540-9309 ; 1540-9295
    ISSN (online) 1540-9309
    ISSN 1540-9295
    DOI 10.1002/fee.2469
    Database NAL-Catalogue (AGRICOLA)

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  10. Article ; Online: Spatiotemporal dispersion compensation for a 200-THz noncollinear optical parametric amplifier.

    Carbery, William P / Bizimana, Laurie A / Barclay, Matthew S / Wright, Nicholas D / Davis, Paul H / Knowlton, William B / Pensack, Ryan D / Arpin, Paul C / Turner, Daniel B

    The Review of scientific instruments

    2024  Volume 95, Issue 3

    Abstract: A noncollinear optical parametric amplifier (NOPA) can produce few-cycle femtosecond laser pulses that are ideally suited for time-resolved optical spectroscopy measurements. However, the nonlinear-optical process giving rise to ultrabroadband pulses is ... ...

    Abstract A noncollinear optical parametric amplifier (NOPA) can produce few-cycle femtosecond laser pulses that are ideally suited for time-resolved optical spectroscopy measurements. However, the nonlinear-optical process giving rise to ultrabroadband pulses is susceptible to spatiotemporal dispersion problems. Here, we detail refinements, including chirped-pulse amplification (CPA) and pulse-front matching (PFM), that minimize spatiotemporal dispersion and thereby improve the properties of ultrabroadband pulses produced by a NOPA. The description includes a rationale behind the choices of optical and optomechanical components, as well as assessment protocols. We demonstrate these techniques using a 1 kHz, second-harmonic Ti:sapphire pump configuration, which produces ∼5-fs duration pulses that span from about 500 to 800 nm with a bandwidth of about 200 THz. To demonstrate the utility of the CPA-PFM-NOPA, we measure vibrational quantum beats in the transient-absorption spectrum of methylene blue, a dye molecule that serves as a reference standard.
    Language English
    Publishing date 2024-03-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 209865-9
    ISSN 1089-7623 ; 0034-6748
    ISSN (online) 1089-7623
    ISSN 0034-6748
    DOI 10.1063/5.0187338
    Database MEDical Literature Analysis and Retrieval System OnLINE

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