JILA Auditorium

Gas flows and metal enrichment in and around simulated galaxies

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Abstract: Galaxies are intimately connected to the environments they live in. The haloes around them contain the gas reservoir from which the galaxies grow, while galactic outflows heat and enrich this circumgalactic medium (CGM). The elemental abundances of present-day stars are, in part, set by these cosmic gas flows. Using zoom-in cosmological simulations of galaxies, I will discuss the physical and observable properties of gas and stars in and around galaxies.

The Dark Energy Spectroscopic Instrument First Year Results: Cosmic Expansion History with Baryon Acoustic Oscillations

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Abstract: The Dark Energy Spectroscopic Instrument (DESI) collaboration is conducting a 5 year redshift survey of 40 million extra-galactic sources over 14,000 square degrees of the northern sky. One of its primary goals is to measure the cosmic expansion history with baryon acoustic oscillations (BAO). I will present the measurement of BAO in galaxy, quasar and Lyman-alpha forest tracers from the first year of observation.

Fundamental Reaction Kinetics Studies for Low-Temperature Astrochemistry Applications

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Abstract:  Many of the new molecules discovered in astrophysical objects are totally outlandish by traditional perspectives: long linear unsaturated carbon chains, metals in surprising charge states, and strained ring structures have all challenged chemists to think beyond terrestrial conventions in explaining how these molecules form and react, and where they fit into the overall cycle of planetary and stellar evolution.

New Insights into the Impact of Water on the Reactivity Of Criegee Intermediate Reactions

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Abstract: Biogenic emissions contribute significantly to the composition and chemistry of the troposphere, with vegetation being the main source of volatile alkenes. For example, isoprene is emitted by plants during photosynthesis and is one of the most abundant organic compounds released into the atmosphere: around 500 Tg of isoprene is emitted annually and forms the largest fraction of non-methane hydrocarbon emissions. The dominant mechanisms for the atmospheric removal of alkenes are reactions with the OH radical and ozone.

Following and controlling nanoscale formation and function of bottom-up assembled materials

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Abstract: Short-range-interacting particles can in principle crystallize via so-called non-classical pathways invoking a metastable liquid intermediate, yet non-equilibrium gelation often occurs before a metastable liquid can form. Using in situ X-ray scattering, we nevertheless watch electrostatically stabilized colloidal semiconducting nanocrystals self-assemble into long-range-ordered superlattices via this non-classical pathway and show how the pathway increases the rate of crystallization over that of direct crystallization from the colloidal phase.

How driving force and charge transfer distance control free charge generation at donor/acceptor interfaces

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Abstract:  I present evidence that electron-transfer in model organic photovoltaic blends can be modeled as a competition between short and long-range electron transfer events, each described by a Marcus parabola having different reorganization energies for the most localized charge-transfer (CT) state and the mobile free charge (CT) state.

Spatial and Temporal Dynamics of Excitons in Van der Waals Heterostructures

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Abstract: Atomically thin van der Waals crystals like graphene and transition metal dichalcogenides allow for the creation of arbitrary, atomically precise heterostructures simply by stacking disparate monolayers without the constraints of covalent bonding or epitaxy. While these are commonly described as nanoscale LEGO blocks, many intriguing phenomena have been discovered in the recent past that go beyond this simple analogy.