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Dichroism Program

When materials absorb soft x-rays,* they experience electronic excitations from tightly bound core states to empty, low-energy valence-band states characterized by lattice symmetry, electronic configuration (charge state, orbital occupation), and magnetic order. X-ray absorption depends strongly on the x-ray polarization (linear, circular) and its relative alignment to the local environment or symmetry of the absorbing ion (orientation of magnetic moments, electronic orbitals, crystal directions, etc.). Combining polarization-dependent x-ray absorption spectroscopy, scattering, and imaging allows us to develop a detailed picture of the interplay between atomic, electronic, and magnetic degrees of freedom. Time-resolved dichroism measurements utilize the pulsed structure of the ALS x-ray beam (70 ps x-ray pulses, every 2 ns) and provide unique opportunities to study, for example, magnetization dynamics and the flow of spin currents through multilayered spintronic devices.

Our research includes the intriguing physics of correlated electron systems, prototypical spintronics devices employing the electron spin to store and process digital information, and biomineralization (i.e., magnetic or birefringent materials synthesized by living organisms). We are continuously optimizing our beamlines and endstations—for new fields of study, improved resolution, automation, and ease of use—and developing novel instruments to enable exploration of exciting physical mechanisms underlying functional materials.

* Typical range: 400–2000 eV (or about 0.6–3 nm in wavelength)

Beamlines

Personnel

ALS Staff

Alpha N'Diaye

Staff Scientist, Interim Program Lead

Barat Achinuq

Project Scientist

Christoph Klewe

Research Scientist

Doctoral and Postdoctoral Researchers

Program Alumni

  • Elke Arenholz, Director, National Synchrotron Light Source II
    Postdoctoral Researcher, Dichroism Program Lead (2000-2019)

  • Juan Felipe Builes, EDF Renewables
    DOE SULI Intern (2014-2015)

  • Samantha Bustamante
    ASPIRES Intern (2022), Cal State University East Bay

  • Rajesh Chopdekar, Technologist, Western Digital
    Project Scientist (2021)

  • Alejandro Cruz, Florida Department of Environmental Protection
    Senior Engineering Scientific Associate (2006-2017)

  • Ingrid Hallsteinsen, Associate Professor, Department of Electronic Systems, Norwegian Institute of Science and Technology
    ALS Doctoral Fellow in Residence (2016-2017), Postdoctoral Researcher (2017-2019)

  • Guanhua (Tibbers) Hao
    Machine Learning Exchange Project Postdoctoral Fellow (2021-2024), ALS Computing Group
    ALS Doctoral Fellow in Residence (2019-2020), University of Nebraska–Lincoln

  • Qing (Helen) He, Lecturer, Department of Physics, Durham University
    Postdoctoral Researcher (2015-2016)

  • Catherine Jenkins, Ejenta Inc.
    Research Scientist (2009-2013)

  • Roland Koch, KLA Tencor
    Research Scientist (2021)

  • Marco Liberati, Manz USA Inc.
    Project Scientist (2008-2010)

  • Cinthia Piamonteze, Scientist, Paul Scherrer Institute
    Postdoctoral Researcher (2004-2007)

  • Derek Reitz, Ph.D. Student, Physics & Astronomy Department, UCLA
    DOE SULI Intern (2017)

  • Padraic Shafer, Computational Scientist/Group Lead, NSLS-II
    Staff Scientist, Dichroism Program Lead (2009-2023)

  • Samuel Slöetjes, Postdoctoral Researcher, Department of Physics & Astronomy, Uppsala University
    ALS Doctoral Fellow in Residence (2016-2018), Norwegian University of Science and Technology

  • Jorge Miguel Soriano, SmarAct Inc.
    Project Scientist

  • Andres Urrea
    ASPIRES Intern (2022), Cal State University East Bay

  • Zhuyun (Maggie) Xiao, Ph.D. Candidate, Electrical and Computer Engineering, UCLA
    ALS Doctoral Fellow in Residence (2018-2019), UCLA

  • Jan-Chi Yang, Assistant Professor, Department of Physics, National Cheng Kung University
    ALS Doctoral Fellow in Residence (2013-2014), National Chiao Tung University

  • Xin Zhang, Research Supervisor, X-Ray Optical Systems
    ALS Doctoral Fellow in Residence (2016), University of Nebraska–Lincoln