About

James D. Gaynor is a Principal Investigator and Assistant Professor of Chemistry at Northwestern University. His role involves leading research efforts within The Gaynor Group, focusing on chemical sciences. The page provides his contact information, including his email and office phone number, but does not include specific details about his research focus, background, or key contributions.

Research topics

• Optics
• Physics
• Atomic physics
• Molecular physics
• Chemical physics
• Chemistry
• Quantum mechanics
• Condensed matter physics
• Photochemistry
• Physical chemistry

Selected publications

• Vibronic DynamicsLocalize Charge in PhotoexcitedCoFe Prussian Blue Analogue Nanoparticles

  Figshare · 2026-03-02

  articleSenior author

  Prussian Blue analogues are prototype photoswitchable materials for understanding how electron spin and charge density evolve in nonequilibrium photoexcited states. Great interest in photomagnetism has driven substantial investigation of ultrafast electronic dynamics, but a sufficient understanding of how molecular-level vibronic dynamics influences spin-related photochemistry in these materials is needed. Here, the dynamics of CsCoFe Prussian Blue analogue nanoparticles are studied with transient infrared absorption spectroscopy probing the photoexcited CN stretch vibration using tunable excitation pulses spanning 350 to 700 nm, paired with first-principles density functional theory analysis to understand the molecular nature of the electronic excited states. Regardless of excitation wavelength, all initially prepared excited states converge to the same metal-to-metal charge-transfer manifold within 300 fs, which then efficiently populates a metal-to-ligand charge-transfer state within 500 fs, localizing the charge onto bridging CN ligands. This study highlights that the electronic, spin, and structural degrees of freedom work together to collectively determine how charge is distributed in CsCoFe nanoparticles.

  DOI

• Vibronic DynamicsLocalize Charge in PhotoexcitedCoFe Prussian Blue Analogue Nanoparticles

  Figshare · 2026-03-02

  datasetSenior author

  Prussian Blue analogues are prototype photoswitchable materials for understanding how electron spin and charge density evolve in nonequilibrium photoexcited states. Great interest in photomagnetism has driven substantial investigation of ultrafast electronic dynamics, but a sufficient understanding of how molecular-level vibronic dynamics influences spin-related photochemistry in these materials is needed. Here, the dynamics of CsCoFe Prussian Blue analogue nanoparticles are studied with transient infrared absorption spectroscopy probing the photoexcited CN stretch vibration using tunable excitation pulses spanning 350 to 700 nm, paired with first-principles density functional theory analysis to understand the molecular nature of the electronic excited states. Regardless of excitation wavelength, all initially prepared excited states converge to the same metal-to-metal charge-transfer manifold within 300 fs, which then efficiently populates a metal-to-ligand charge-transfer state within 500 fs, localizing the charge onto bridging CN ligands. This study highlights that the electronic, spin, and structural degrees of freedom work together to collectively determine how charge is distributed in CsCoFe nanoparticles.

  DOI

• Vibronic DynamicsLocalize Charge in PhotoexcitedCoFe Prussian Blue Analogue Nanoparticles

  Figshare · 2026-03-02

  datasetSenior author

  Prussian Blue analogues are prototype photoswitchable materials for understanding how electron spin and charge density evolve in nonequilibrium photoexcited states. Great interest in photomagnetism has driven substantial investigation of ultrafast electronic dynamics, but a sufficient understanding of how molecular-level vibronic dynamics influences spin-related photochemistry in these materials is needed. Here, the dynamics of CsCoFe Prussian Blue analogue nanoparticles are studied with transient infrared absorption spectroscopy probing the photoexcited CN stretch vibration using tunable excitation pulses spanning 350 to 700 nm, paired with first-principles density functional theory analysis to understand the molecular nature of the electronic excited states. Regardless of excitation wavelength, all initially prepared excited states converge to the same metal-to-metal charge-transfer manifold within 300 fs, which then efficiently populates a metal-to-ligand charge-transfer state within 500 fs, localizing the charge onto bridging CN ligands. This study highlights that the electronic, spin, and structural degrees of freedom work together to collectively determine how charge is distributed in CsCoFe nanoparticles.

  DOI

• Vibronic Dynamics Localize Charge in Photoexcited CoFe Prussian Blue Analogue Nanoparticles

  The Journal of Physical Chemistry Letters · 2026-03-02

  articleSenior authorCorresponding

  Prussian Blue analogues are prototype photoswitchable materials for understanding how electron spin and charge density evolve in nonequilibrium photoexcited states. Great interest in photomagnetism has driven substantial investigation of ultrafast electronic dynamics, but a sufficient understanding of how molecular-level vibronic dynamics influences spin-related photochemistry in these materials is needed. Here, the dynamics of CsCoFe Prussian Blue analogue nanoparticles are studied with transient infrared absorption spectroscopy probing the photoexcited CN stretch vibration using tunable excitation pulses spanning 350 to 700 nm, paired with first-principles density functional theory analysis to understand the molecular nature of the electronic excited states. Regardless of excitation wavelength, all initially prepared excited states converge to the same metal-to-metal charge-transfer manifold within 300 fs, which then efficiently populates a metal-to-ligand charge-transfer state within 500 fs, localizing the charge onto bridging CN ligands. This study highlights that the electronic, spin, and structural degrees of freedom work together to collectively determine how charge is distributed in CsCoFe nanoparticles.

  PublisherDOI

• Vibronic DynamicsLocalize Charge in PhotoexcitedCoFe Prussian Blue Analogue Nanoparticles

  Figshare · 2026-03-02

  articleSenior author

  Prussian Blue analogues are prototype photoswitchable materials for understanding how electron spin and charge density evolve in nonequilibrium photoexcited states. Great interest in photomagnetism has driven substantial investigation of ultrafast electronic dynamics, but a sufficient understanding of how molecular-level vibronic dynamics influences spin-related photochemistry in these materials is needed. Here, the dynamics of CsCoFe Prussian Blue analogue nanoparticles are studied with transient infrared absorption spectroscopy probing the photoexcited CN stretch vibration using tunable excitation pulses spanning 350 to 700 nm, paired with first-principles density functional theory analysis to understand the molecular nature of the electronic excited states. Regardless of excitation wavelength, all initially prepared excited states converge to the same metal-to-metal charge-transfer manifold within 300 fs, which then efficiently populates a metal-to-ligand charge-transfer state within 500 fs, localizing the charge onto bridging CN ligands. This study highlights that the electronic, spin, and structural degrees of freedom work together to collectively determine how charge is distributed in CsCoFe nanoparticles.

  DOI

• Capturing Ring Opening in Photoexcited Enolic Acetylacetone upon Hydrogen Bond Dissociation by Ultrafast Electron Diffraction

  The Journal of Physical Chemistry Letters · 2025-05-14 · 3 citations

  articleOpen access

  Photoinduced biological and chemical reactions are often based on key structural transformations of a molecule driven across multiple electronic states. Acetylacetone (AcAc) is a prototypical system for complex chemical pathways involving several conical intersections (CI) and singlet–triplet intersystem crossings (ISC) characterized by distinct geometries. In the gas phase, AcAc is predominantly in a planar ring-like enolic form stabilized by a strong intramolecular O–H···O hydrogen bond. Following excitation into the S2 (ππ*) state at 266 nm, acetylacetone undergoes rapid internal conversion followed by intersystem crossing. Such relaxation pathways are associated with structural changes including ring opening, deplanarization, and bond elongation. In this work, ultrafast electron diffraction (UED) at the SLAC MeV-UED setup is employed as a direct structural probe with a time resolution of 160 fs. Together with trajectory surface hopping simulations, analysis of the UED data provides a new perspective on the early time nuclear dynamics in acetylacetone. Specifically, AcAc is observed to undergo ring opening, deplanarization, and bond elongation all within the first 700 fs after photoexcitation. The monitored dynamics is associated mainly with the nuclear motion on the S1 potential energy surface, formed after very rapid transfer from S2 to S1, allowing AcAc to reach the conical intersection to intersystem crossing. Such time scales of nuclear motion are contrasted with the time scales of electronic transitions in AcAc that were previously characterized with spectroscopic methods, specifically internal conversion (<100 fs) and intersystem crossing (∼1.5 ps).

  PublisherDOI

• Double-quantum two-dimensional electronic–vibrational spectroscopy: Theory. Vibronic coherences in nonadiabatic phenomena

  The Journal of Chemical Physics · 2025-05-01 · 3 citations

  articleSenior author

  Nonadiabatic phenomena are ubiquitous in polyatomic molecular systems and are responsible for many ultrafast dynamics occurring outside of the Born-Oppenheimer approximation. In particular, electronic curve crossings offer ultrafast, sub-100 fs pathways for efficient electronic relaxation between potential energy surfaces, where the electronic and vibrational degrees of freedom become strongly coupled. Due to the unique mixture of temporal and spectral resolution required to detect electronic curve crossings, experimental observation has remained a considerable challenge. Here, double-quantum coherence two-dimensional electronic-vibrational (2Q 2D EV) spectroscopy is introduced for the first time and proposed as an experimental approach to monitor vibronic dynamics near and at electronic curve crossings directly through vibronic coherences using a mixture of broadband visible and infrared pulses. A semi-classical vibronic Hamiltonian is used that characterizes the parametrically defined coupling between high-frequency vibrations and low-frequency vibrational modes involved in tuning electronic potential energy surfaces. This work displays how unique multidimensional pulse sequences can uncover dynamics that are hidden in conventional techniques.

  PublisherDOI

• Towards understanding ligand-nanoparticle photochemistry with ultrafast electronic-vibrational spectroscopy

  2024-09-30

  article1st authorCorresponding

  Photochemical processes in complex molecules and materials are central to controlling the movement of charge and energy on the microscopic level. The ability to tailor the motion of charge through synthetic modification enables new material properties to be realized. Dynamic couplings and correlations occurring on ultrafast timescales between the electronic motions of the system and the microscopic structure of the system are key aspects to understand in order to discover new photoinduced and optoelectronic behaviors in molecules and materials. In nanoparticle systems and colloidal suspensions, the capping ligands can be used both to stabilize the material and to tune optoelectronic properties of the materials. This paper discusses studies using femtosecond transient-IR absorption spectroscopy and two-dimensional electronic-vibrational (2D EV) spectroscopy on Co-CN-Fe (i.e., Prussian blue analogue) nanoparticles with polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) stabilizing ligands. These mixed-valence, mixed-metal nanoparticle systems contain broad and complex electronic absorption features with different charge transfers accessible throughout the UV and visible spectral region. The cyano bridging ligand stretching vibration is a sensitive reporter of charge transfer dynamics that is used in this study to directly probe how photoinduced charge motion in 11 nm Co-CN-Fe nanoparticles occurs. The initial data discussed in this paper show different CN stretching dynamics and spectral features are observed that are capping ligand dependent. The results of this study suggest that ultrafast electronic-vibrational spectroscopies will be crucial methods to understand vibronic coupling dynamics in complex systems, such as nanoparticle-ligand materials.

  PublisherDOI

• Capturing ring opening in photoexcited enolic acetylacetone upon hydrogen bond dissociation by ultrafast electron diffraction

  Research Square · 2024-01-23 · 1 citations

  preprintOpen access
  PublisherOA PDFDOI

• Dynamics via Attosecond Four-Wave Mixing

  Springer proceedings in physics · 2024-01-01

  book-chapterOpen access1st authorCorresponding

  Abstract Attosecond four-wave mixing spectroscopy is a relatively new technique for studying ultrafast dynamics of highly excited states with exquisite temporal precision and spectral resolution. The attosecond four-wave mixing technique, as described in this paper, uses non-collinear beam geometries of one attosecond pulse together with two optical pulses to obtain background-free, spatially isolated emission signals in the extreme ultraviolet range that directly resolve coherent dynamics in the time domain. This method is advantageous by avoiding the strong spectral modulations that often complicate the interpretation of collinear attosecond transient absorption studies while also enabling greater control over the spatial and temporal characteristics of each light-matter interaction used to probe the ultrafast processes. This paper describes a broad range of attosecond four-wave mixing experiments performed in gas phase atoms and molecules, and a recent extension into solids.

  PublisherOA PDFDOI

Frequent coauthors

• Ashley P. Fidler

  University of California, Berkeley

  31 shared

• Stephen R. Leone

  Lawrence Berkeley National Laboratory

  31 shared

• Yen-Cheng Lin

  University of California, Berkeley

  25 shared

• Daniel M. Neumark

  University of California, Berkeley

  23 shared

• Munira Khalil

  University of Washington

  22 shared

• Valeriu Scutelnic

  14 shared

• Jie Yang

  10 shared

• Kristina F. Chang

  10 shared

Labs

• The Gaynor GroupPI

Education

• Ph.D., Chemistry

  University of California, Berkeley

  1986

• B.S., Chemistry

  University of California, Los Angeles

  1981

Awards & honors

• APS Division of Chemical Physics Early Career Member at Larg…
• American Chemical Society Young Investigator Award – ACS Phy…
• Arnold O. Beckman Postdoctoral Fellowship – Beckman Foundati…
• Schmidt Science Fellowship Finalist (2020)
• Carl E. Anderson Dissertation Award – American Physical Soci…