PhD Defense Public Talk
Apr
6
2026
Apr
6
2026
Description
Spectral Line Shapes in Dense Stellar Plasmas
Spectral line shapes describe the distribution of opacity from bound electronic transitions. Accurate line shape theory is therefore a necessary input for modeling photon transport through the wide range of plasma environments found in stars. Stark broadening, where charged particles perturb the electronic structure of radiating atoms, is often the dominant broadening mechanism in stars, including many stellar photospheres that can be directly observed, and stellar interiors like that of our own sun. Observations of white dwarf star photospheres and helioseismic oscillations, as well as high-energy-density laboratory opacity experiments conducted at the Sandia Z-Machine and the Lawrence Livermore National Ignition Facility, have recently suggested that serious discrepancies persist between modern Stark-broadened line shape models and reality. We attempt to improve Stark broadening theory in similar dense stellar plasmas by exploring novel techniques for incorporating detailed electronic structure into line shape calculations. In this talk we discuss our new pseudoatom-based molecular dynamics approach for calculating plasma microfields, or low-frequency electric field distributions, that moves beyond a Yukawa-type screening prescription, and introduce electron configuration transitions into these simulations to demonstrate how allowing for such transitions can generate absorption-emission line shape asymmetries, even in steady-state plasmas. We then discuss our new multi-basis approach to the simulation line shape method that considers quasi-molecular structure during close ion collisions, highlight our implementation of new line shapes with quasi-H2+ features into a stellar atmosphere spectral synthesis code, and demonstrate how this method compares to spectra from hydrogen-atmosphere white dwarf stars.
Other Events in This Series
Apr
11
2025
Lindsay House PhD Defense
PhD Defense Talk by graduate student Lindsay House
9:00 am – 10:00 am • In Person
Speaker(s): Lindsay House - The University of Texas at Austin
Apr
22
2025
Olivia Cooper PhD Defense Talk
PhD Defense Talk by graduate student Olivia Cooper
10:00 am – 11:00 am • In Person
Speaker(s): Olivia Cooper - The University of Texas at Austin
Jun
3
2025
Melanie Rowland PhD Defense
PhD defense talk
2:00 pm – 3:00 pm • In Person
Speaker(s): Melanie Rowland - The University of Texas at Austin
Jun
11
2026
PhD Defense Public Talk
Oscar Chavez Ortiz PhD Defense Public Talk
2:00 pm – 3:00 pm • In Person
Speaker(s): Oscar Chavez Ortiz - The University of Texas at Austin
Jun
22
2026
PhD Defense Public Talk
Hollis Akins PhD Defense Public Talk
2:00 pm – 3:00 pm • In Person
Speaker(s): Hollis Akins - The University of Texas at Austin
Jul
1
2026
PhD Defense Public Talk
Alexa Morales PhD Defense Public Talk
9:30 am – 10:30 am • In Person
Speaker(s): Alexa Morales - The University of Texas at Austin
Jul
17
2026
PhD Defense Public Talk
Katherine Chworowsky PhD Defense Public Talk
10:00 am – 11:00 am • In Person
Speaker(s): Katherine Chworowsky - The University of Texas at Austin
Jul
23
2026
PhD Defense Public Talk
Kay Guo PhD Defense Public Talk
10:00 am – 11:00 am • In Person
Speaker(s): Kay Guo - The University of Texas at Austin
Jul
24
2026
PhD Defense Public Talk
Kaelee Parker PhD Defense Public Talk
10:00 am – 11:00 am • In Person
Speaker(s): Kaelee Parker - The University of Texas at Austin
Aug
3
2026
PhD Defense Public Talk
Saiyang Zhang PhD Defense Public Talk
12:00 pm – 1:00 pm • In Person
Speaker(s): Saiyang Zhang - The University of Texas at Austin