Phys Chem/Chem Phys Seminar

The interaction of the electronic spin and molecular vibrations mediated by spin-orbit coupling governs spin relaxation in molecular qubits. We derive a dynamic molecular spin Hamiltonian that includes both adiabatic and non-adiabatic spin-dependent interactions, and we implement the computation of its matrix elements using density functional theory. The dynamic molecular spin Hamiltonian contains a novel spin-vibronic interaction with non-adiabatic origin in addition to the conventional molecular Zeeman and dipolar spin interactions with adiabatic origin.

For the overwhelming majority of organisms, effective communication and coordination are critical in the quest to survive and reproduce. A better understanding of these processes can benefit from physics, mathematics, and computer science – via the application of concepts like energetic cost, compression (minimization of bits to represent information), and detectability (high signal-to-noise-ratio). My lab's goal is to formulate and test phenomenological theories about natural signal design principles and their emergent spatiotemporal patterns.

Surfaces and interfaces play a crucial role in chemical and physical phenomena, such as heterogeneous catalysis and reactions. At the surface or interface of water, the hydrogen-bonded network is abruptly interrupted, giving rise to fascinating interfacial properties. These specific properties are the driving forces for many biochemical, environmental and geochemical processes.

Einstein’s relationships between absorption and emission line spectra in vacuum[1] have a conflict between infinitely narrow lines, a finite spontaneous emission rate, and the time-energy uncertainty principle.

All chemical reactions are controlled by species we rarely detect: short-lived carbenes, radicals, and ketenes steer reaction pathways and ultimately determine selectivity and yield. Conventional tools such as GC/MS or NMR usually miss intermediates, even though mechanistic insight is urgently needed for rational process optimization.

Over the last 20 years, we have discovered that we live in a molecular Universe: A Universe with a rich and varied organic inventory; A Universe where molecules are abundant and widespread; A Universe where molecules play a central role in key processes that dominate the structure and evolution of galaxies. A Universe where molecules provide convenient thermometers and barometers to probe local physical conditions.

Linear spectroscopy is used to learn about transitions from the ground states of systems. Nonlinear spectroscopies, such as transient absorption (TA) spectroscopy, first excite the system and then probe after some time delay, giving dynamical information about excited states and spectral information about their excitations. If the pump pulses are strong enough, then some molecules are excited multiple times, and the signal has contributions from singly excited molecules mixed with those from multiply excited molecules.

Abstract: Modeling gas-phase chemical kinetics relevant to combustion and atmospheric chemistry requires a complete description of elementary reactions involving ephemeral species such as hydroperoxyalkyl radicals, Q̇OOH, which undergo competing sets of unimolecular reactions and bimolecular reactions with O2. The balance of flux from the competition affects rates of chain-branching and inherently depends on temperature, pressure, and oxygen concentration.

Quantum interferences, where two electronic pathways “compete” in a manner akin to the interference of separate propagating waves, are often exploited in atomic systems to realize a variety of exotic phenomena, such as electromagnetically induced transparency, slow light and lasing without inversion. In crystalline materials, quantum interferences can sometimes be difficult to discern with conventional probes, even if their consequences may be just as profound.

Mid-Infrared (MIR) light can interact with molecules by selectively exciting molecular vibrational modes. In combination with photonic structures, MIR can target specific vibrational states of molecular to influence chemical reactions. In this talk, I will explain how photonic environments can modify molecular dynamics through strong light-matter coupling. This strong coupling leads to the molecular vibrational polaritons – a hybrid quasiparticle between light and matter.