Nan Liu
Postdoctoral Fellow

Nan Liu

Research Interests

Isotopic studies of presolar grains; stellar nucleosynthesis in different types of stars; formation of presolar grains in stellar environments; isotopic anomalies in meteorites and their connections to those different types of presolar grains.

Academics

B.E., Environmental Science, University of Science and Technology of China, 2009 Ph.D., Cosmochemistry, University of Chicago, 2014

Contact & Links

  • (202) 478-8483 | fax: (202) 478-8821
  • nliu at carnegiescience.edu
  • Department of Terrestrial Magnetism
    Carnegie Institution of Washington
    5241 Broad Branch Road, NW
    Washington, DC 20015-1305
  • curriculum vitae
  • Publications

Overview

Nan Liu
Left panel: An SEM image of a presolar mainstream SiC grain extracted from Murchison meteorite; Right panel: four-isotope plots of correlated δ(88Sr/86Sr) versus δ(135Ba/136Ba). The mainstream SiC grain data measured using resonance ionization mass spectrometry (RIMS) are shown as black dots with 2σ err. Nucleosynthetic model predictions for a 2 M_sun, 0.5 Z_sun asymptotic giant branch (AGB) star evolve from its original composition (zero) towards different s-process end members, depending on adopted neutron exposure strengths. Each model prediction evolves from oxygen-rich ambient (lines) towards carbon-rich (lines with symbols) because of 12C production via He burning (triple alpha reaction) in the He shell.

Nan Liu is interested in isotope studies of presolar grains (left image), which are condensed dusts during stellar winds and/or explosions that were ejected to the interstellar medium, and became part of the proto-solar cloud from which the Sun formed. Isotopic composition of such grains allows studies of nucleosynthesis in their parent stars at a level of detail that is unavailable to spectroscopic observation. 

For her Ph.D. research, she focused on isotope analysis of s (slow neutron capture)-process elements in single presolar SiC grains (right image) using the CHARISMA instrument by Resonance Ionization Mass Spectrometry (RIMS) at Argonne National Laboratory. Such in situ isotope analysis of heavy elements in mainstream type grains from asymptotic giant branch (AGB) stars allowed derivation of new constraints on the “13C-pocket” that is the main neutron source for the s-process in AGB stars.

At DTM, she plans to extend her research to isotope studies of other types of presolar grains, which came from various types of stars and can be used to study other nucleosynthetic processes in their parent stars. These grains are rare and need extensive search using the NanoSIMS instrument for isotopic compositions of light elements (e.g., C and Si). In addition to constrain different nucleosynthetic processes in stars, she is also interested in exploring the connection between the origin of the solar system (isotopic anomalies found in primitive meteorites) and isotopic compositions of the presolar grains.