We examine the recently reported first synthesis of the elusive low-valent vanadium(III) in a vanadium oxo complex with a computation representing 10(21) quantum degrees of freedom. While this computation is intractable with a conventionally constructed wave function, it is performed here by a direct calculation of the system's two-electron reduced density matrix (2-RDM), where the 2-RDM is constrained by nontrivial conditions, known as N-representability conditions, that restrict the 2-RDM to represent an N electron quantum system. We show that the added (reducing) electron becomes entangled among the five pyridine ligands. While smaller calculations predict a metal-centered addition, large-scale 2-RDM calculations show that quantum entanglement redirects the electron transfer to the pyridine ligands, resulting in a ligand-centered addition. Beyond its implications for the synthesis of low-valent vanadium oxo complexes, the result suggests new possibilities for using quantum entanglement to predict and control electron transfer in chemical and biological materials.

We study resonance energy transfer between a donor–acceptor pair located on opposite sides of a spherical silver nanoparticle and explore the dependence of energy-transfer rate on nanoparticle size using a quantum electrodynamics theory we developed previously. This theory indicates that the rate is determined by the product of donor emission spectra, acceptor absorption spectra, and an electronic coupling factor (CF) that is determined by electrodynamics associated with the donor as a dipole emitter near the nanoparticle. We find that the CF spectra show peaks that are associated with localized surface plasmon resonances, but the locations of the most significant peaks are less correlated to the size of the nanoparticle than is found for extinction spectra for the same particle. For small nanoparticles (≲30 nm), where dipole plasmon excitation dominates, a quasi-static analysis leads to an analytical formula, in which the CF peaks and dips involve interference between donor electric field and the scattered dipolar field of the nanoparticle. For larger nanoparticles (60–210 nm), the CF maximizes at a wavelength near 355 nm independent of particle size that is determined by the highest multipole plasmon that contributes significantly to the extinction spectrum, with only small contributions arising from lower multipole plasmons, such as the dipole plasmon. Also, for wavelengths near 325 nm where the bulk plasmon resonance of silver can be excited, surface plasmons cannot be excited, so excitation from the donor cannot be transmitted by surface plasmons to the acceptor, leading to a pronounced dip in the CF. This work provides new concepts concerning plasmon-mediated energy transfer that are quite different from conventional (Förster) theory, but which should dominate energy-transfer behavior when donor and acceptor are sufficiently separated.

A computational method to model diffraction-limited images from super-resolution surface-enhanced Raman scattering microscopy is introduced. Despite significant experimental progress in plasmon-based super-resolution imaging, theoretical predictions of the diffraction limited images remain a challenge. The method is used to calculate localization errors and image intensities for a single spherical gold nanoparticle-molecule system. The light scattering is calculated using a modification of generalized Mie (T-matrix) theory with a point dipole source and diffraction limited images are calculated using vectorial diffraction theory. The calculation produces the multipole expansion for each emitter and the coherent superposition of all fields. Imaging the constituent fields in addition to the total field provides new insight into the strong coupling between the molecule and the nanoparticle. Regardless of whether the molecular dipole moment is oriented parallel or perpendicular to the nanoparticle surface, the anisotropic excitation distorts the center of the nanoparticle as measured by the point spread function by approximately fifty percent of the particle radius toward to the molecule. Inspection of the nanoparticle multipoles reveals that distortion arises from a weak quadrupole resonance interfering with the dipole field in the nanoparticle. When the nanoparticle-molecule fields are in-phase, the distorted nanoparticle field dominates the observed image. When out-of-phase, the nanoparticle and molecule are of comparable intensity and interference between the two emitters dominates the observed image. The method is also applied to different wavelengths and particle radii. At off-resonant wavelengths, the method predicts images closer to the molecule not because of relative intensities but because of greater distortion in the nanoparticle. The method is a promising approach to improving the understanding of plasmon-enhanced super-resolution experiments.

Based on our long-standing Intensive Training Program for Effective Teaching Assistants in Chemistry, we have developed an Advanced Training Course for Teachers and Researchers in Chemistry at The University of Chicago. The topics in this course are designed to train graduate teaching assistants (GTAs) to become effective teachers and well-rounded PhD candidates.The goals of the course are to build ethics, critical thinking, and a positive self-image as a teacher through the use of a variety of pedagogical tools. Concurrently, the GTAs are transitioned into independent researchers with the skills to prepare written reports and oral presentations. The goals of this course were achieved based on the results of participant feedback. The experience gained and issues identified from the course may be used to guide future training courses.

Quantum molecular dynamics requires an accurate representation of the molecular potential energy surface from a minimal number of electronic structure calculations, particularly for nonadiabatic dynamics where excited states are required. In this paper, we employ pseudospectral sampling of time-dependent Gaussian basis functions for the simulation of non-adiabatic dynamics. Unlike other methods, the pseudospectral Gaussian molecular dynamics tests the Schrödinger equation with N Dirac delta functions located at the centers of the Gaussian functions reducing the scaling of potential energy evaluations from O(N 2 ) to O(N ). By projecting the Gaussian basis onto discrete points in space, the method is capable of efficiently and quantitatively describing nonadiabatic population transfer and intra-surface quantum coherence. We investigate three model systems; the photodissociation of three coupled Morse oscillators, the bound state dynamics of two coupled Morse oscillators, and a two-dimensional model for collinear triatomic vibrational dynamics. In all cases, the pseudospectral Gaussian method is in quantitative agreement with numerically exact calculations. The results are promising for nonadiabatic molecular dynamics in molecular systems where strongly correlated ground or excited states require expensive electronic structure calculations.