Revisiting Sub-Band Gap Emission Mechanism in 2D Halide Perovskites: The Role of Defect States
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Engineering topics
Neukirch, Amanda J.
Publications and source records attributed to Neukirch, Amanda J..
Ground and Excited Electronic Structure Analysis of CH Diatomic Molecule and Its Astrophysical Importance [Slides]
Ground and excited PECs and DMCs of CH are reported. The aug-cc-pV6Z basis set is a good accuracy-efficiency compromise to study C-H system. CASSCF results are in reasonable agreement with the experiment. High-level MRCI analysis are vital for reaching for the experimental accuracy.
79 ASTRONOMY AND ASTROPHYSICS↗
Stabilization of Charge-Transfer Excited States in Biological Systems: A Computational Focus on the Special Pair in Photosystem II Reaction Centers
Charge-transfer (CT) excited states play an important role in many biological processes. However, many computational approaches often inadequately address the equilibration effects of nuclear and environmental degrees of freedom on these states. One prominent example of systems in which CT states are of utmost importance is reaction centers (RC) in photosystems. Here we use a multiscale approach combined with time-dependent density functional theory to explore the lowest CT excited state of the special pair P D1 –P D2 in the Photosystem II-RC of a cyanobacterium. We find that the nonequilibrium CT excited state resides near the Soret band, making an exciton the lowest-energy excited state. However, accounting for nuclear and state-specific dielectric equilibration along the CT potential energy surface (PES), the CT state P D1 – –P D2 + stabilizes energetically below the excitonic state. Importantly, this underscores the crucial role of state-specific solvation in mapping the PES of CT states, as demonstrated in a simplified dimer model.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Investigation on laser absorption and x-ray radiation in microstructured titanium targets heated by short-pulse relativistic laser pulses
The enhancement effect of a microstructured surface on laser absorption and characteristic Kα emission has been investigated by measuring K-shell emission from titanium (Ti) targets irradiated with high-intensity (~10 20 W cm -2 ), subpicosecond (500 fs) laser pulses. The experimental results indicate a modest enhancement (1.6×) of Kα emission from microstructured targets compared to flat foils, but with a similar intensity and profile of Heα and Li-like satellites. Particle-in-cell (PIC) simulations are implemented to further understand the underlying physical processes in the laser interaction with both targets, interpreting the mechanisms responsible for the Kα enhancement. The reasons for the lower-than-expected enhancement of Kα emission are discussed. The rapid heating of the bulk plasma might result in the premature shutdown of Kα emission before the thermalization of hot electrons or even the end of laser pulses, suggesting that the use of Kα emission as a diagnostic of the hot-electron yield or relaxation could lead to a misinterpretation.
36 MATERIALS SCIENCE↗
Dielectric Screening and Charge-Transfer in 2D Lead-Halide Perovskites for Reduced Exciton Binding Energies
Not Available
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Molecular properties controlling chirality transfer to halide perovskite: computational insights
Computationally investigate chirality transfer effect from chiral ligands bound to the surface of a lead-halide perovskite nanomaterial. By changing the molecular polarity of the chiral molecules, the chirality of the system can be tuned.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A data analysis method to rapidly characterize gallium concentration in plutonium matrices using LIBS
The processing of actinide samples is a complex and costly endeavor that requires compositional analysis at various stages. Laser-induced breakdown spectroscopy (LIBS) has been used to analyze actinide-containing samples in many nuclear applications including waste management, fuel processing and forensics. The LIBS spectrum obtained from actinide materials are generally extremely complex, exhibiting many thousands of strong emission lines. This makes it difficult to identify other elements within the sample of interest, given the rich and dominant actinide spectrum. Here, in this article, we describe a recent effort to identify and quantify impurities and alloying constituents in plutonium matrices using a hand-held LIBS instrument that is used to rapidly and efficiently measure an emission spectrum from a material sample. We tabulate the emission line positions and intensities of plutonium. We report the development of machine-learning software that can identify gallium and quantify its concentration in plutonium matrices. This work has the potential to provide a rapid and nearly non-destructive technique that allows more confidence in characterizing the composition of materials that are present within complex actinide associated targets. We describe how our LIBS measurements and data analysis methods have successfully quantified the gallium concentration in a variety of samples.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Atomic structure considerations for the low-temperature opacity of Xenon
Here, we have begun a preliminary investigation into the opacity of Xe at low temperatures (<50 eV). The emissivity and opacity of Xe is a crucial factor in determining the utility of Xe in EUV lithography, with numerous industrial applications. To this end, we have been exploring the accuracy of some approximations used in opacity models for the relevant ion stages of Xe (6 times ionized through 20 times ionized). Due to the complexity of Xe atomic structure, one needs to use full configuration-interaction to properly describe the strong mixing in the various n=4 sub-shells that give rise to the Δn=0 and Δn=1 transitions that dominate the opacity spectrum at low temperatures. Since calculations that include full configuration-interaction for large numbers of configurations quickly become computationally prohibitive, we have explored hybrid calculations, in which full configuration-interaction is retained for the most important transitions, while intermediate coupling is employed for all other transitions. After verifying atomic structure properties, local-thermodynamic-equilibrium (LTE) opacities are generated using the ATOMIC code at selected temperatures and densities and compared to various experimental results.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗