The phonon-modulated Jahn-Teller distortion of the nitrogen vacancy center in diamond.

The negatively charged nitrogen vacancy (NV) center in diamond is an optically accessible material defect with a unique combination of spin and optical properties that has attracted interest in quantum-information sciences and as a design candidate for nanoscale quantum sensors. Here, we present time-resolved nonlinear optical spectroscopy measurements, conducted with ultrabroadband laser pulses, that reveal strong modulation of the excited-state by the longitudinal optical (LO) phonon of the diamond lattice. The LO phonon and its overtones geometrically distort neighboring NV centers, driving long lived (3.

Spatiotemporal dispersion compensation for a 200-THz noncollinear optical parametric amplifier.

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.

Fluorescence Quenching Effects of Tetrazines and Their Diels-Alder Products: Mechanistic Insight Toward Fluorogenic Efficiency.

Inverse electron demand Diels-Alder reactions between s-tetrazines and strained dienophiles have numerous applications in fluorescent labeling of biomolecules. Herein, we investigate the effect of the dienophile on the fluorescence enhancement obtained upon reaction with a tetrazine-quenched fluorophore and study the possible mechanisms of fluorescence quenching by both the tetrazine and its reaction products. The dihydropyridazine obtained from reaction with a strained cyclooctene shows a residual fluorescence quenching effect, greater than that exerted by the pyridazine arising from reaction with the analogous alkyne.

Frenkel excitons in heat-stressed supramolecular nanocomposites enabled by tunable cage-like scaffolding.

Delocalized Frenkel excitons-coherently shared excitations among chromophores-are responsible for the remarkable efficiency of supramolecular light-harvesting assemblies within photosynthetic organisms. The translation of nature's design principles to applications in optoelectronic devices has been limited by the fragility of the supramolecular structures used and the delicate nature of Frenkel excitons, particularly under mildly changing solvent conditions and elevated temperatures and upon deposition onto solid substrates. Here, we overcome those functionalization barriers through composition of stable supramolecular light-harvesting nanotubes enabled by tunable (~4.

Resolving the Fluorescence Quenching Mechanism of an Oxazine Dye Using Ultrabroadband Two-Dimensional Electronic Spectroscopy.

The design and optimization of fluorescent labels and fluorogenic probes rely heavily on their ability to distinguish among multiple competing fluorescence quenching mechanisms. Cresyl violet, a member of the 1,4-oxazine family of dyes, has generally been regarded as an exemplary fluorescent probe; however, recent ultrafast experiments revealed an excited-state decay kinetic of 1.2 ps, suggesting the presence of a transient photochemical state.

Spin-Orbit Coupling Drives Femtosecond Nonadiabatic Dynamics in a Transition Metal Compound.

Transient absorption measurements conducted using broadband, 6 fs laser pulses reveal unexpected femtosecond dynamics in the [IrBr] model system. Vibrational spectra and the X-ray crystal structure indicate that these dynamics are not induced by a Jahn-Teller distortion, a type of conical intersection typically associated with the spectral features of transition metal compounds. Two-dimensional electronic spectra of [IrBr] contain 23 cross peaks, which necessarily arise from spin-orbit coupling.

Signatures of Herzberg-Teller coupling in three-dimensional electronic spectroscopy.

The coupling between electronic and nuclear variables is a key consideration in molecular dynamics and spectroscopy. However, simulations that include detailed vibronic coupling terms are challenging to perform, and thus a variety of approximations can be used to model and interpret experimental results. Recent work shows that these simplified models can be inadequate.

Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule.

Conical intersections are molecular configurations at which adiabatic potential-energy surfaces touch. They are predicted to be ubiquitous, yet condensed-phase experiments have focused on the few systems with clear spectroscopic signatures of negligible fluorescence, high photoactivity, or femtosecond electronic kinetics. Although rare, these signatures have become diagnostic for conical intersections.

Resolving molecular vibronic structure using high-sensitivity two-dimensional electronic spectroscopy.

Coherent multidimensional optical spectroscopy is an emerging technique for resolving structure and ultrafast dynamics of molecules, proteins, semiconductors, and other materials. A current challenge is the quality of kinetics that are examined as a function of waiting time. Inspired by noise-suppression methods of transient absorption, here we incorporate shot-by-shot acquisitions and balanced detection into coherent multidimensional optical spectroscopy.