NeXUS Newsletter

Winter 2023 Newsletter

Meet the NeXUS Staff

Karen Keller, NeXUS Administrative Support

Karen Keller joined the Ohio State University in fall 2021 as the NeXUS business operations and administrative specialist.  Karen received her MS in Environmental Horticulture from the University of Florida, where she subsequently worked as a biological scientist at the Mid-Florida Research and Education Center. Prior to joining Ohio State, Karen spent 10 years as an administrative director for a nonprofit organization, where she helped to grow the organization’s fundraising and grants programs and developed a passion for supporting teams. Karen looks forward to helping create a successful experience for users of the NeXUS facility.


Fall 2022 Newsletter

2nd NeXUS User Workshop Held July 25-26

Workshop by the Numbers:
120 Virtual attendees to the plenary session
59 Institutions represented
12 Countries represented
20 Working Group panelists



Plenary Sessions:

Anne L’Huillier, Lund University – “Attosecond light pulses for the study of electron dynamics in matter”  Watch recording
David Awschalom, University of Chicago – “The quantum revolution: exploring materials for new technologies”
NeXUS co-director Robert Baker – NeXUS overview and facility updates  Watch recording

A special Thank You to the panelists who attended our in-person Working Groups on July 25 & 26 at The Ohio State University!  These working groups are developing recommendations for first NeXUS science in the fields of:

Quantum Materials and Condensed Matter Physics
Attosecond Electronic and Molecular Dynamics
Liquid Phase and Interfacial Chemical Dynamics
Dynamics in Biological Systems

View Panelist Roster

We thank you for your hard work and enthusiasm in guiding NeXUS forward!







Meet the NeXUS Staff

TJ Ronningen, NeXUS Project Manager

Dr. TJ Ronningen is a Research Scientist in the Electrical and Computer Engineering department and the project manager for NeXUS development. TJ earned his PhD in Chemical Physics from Ohio State, working with Dr. Frank De Lucia on millimeter wave spectroscopy and low-temperature molecular collision dynamics. He then worked as a research scientist for 12 years at Battelle. At Battelle he collaborated on several multi-disciplinary research projects, providing expertise in spectroscopy, chemical analysis, optics, and classification algorithms. During this time, he learned to enjoy a Systems Engineering and Project Management approach to challenging problems.
Dr. Ronningen returned to Ohio State in 2017. At Ohio State his research focuses on the development and application of infrared detectors. This research requires the development of novel semiconductor materials and device structures, and it has applications to remote sensing, hazard detection, and lidar imaging. As part of his research, TJ supports several multi-institution projects as a test lead, systems engineer, or project manager. TJ is currently serving as chair of Out to Innovate, a professional society supporting LGBTQ+ people in STEM fields.


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System Spotlight –
The NeXUS Scanning Tunneling Microscope (STM) End Station

The scanning tunneling microscope (STM) end station combines the atomic scale spatial and electronic characterization capabilities of an STM with XUV light to add elemental contrast and ultra-fast temporal resolution. While STM has matured into an essential tool in nanoscience, a lack of element-specificity in imaging, and poor time resolution remains a challenge with typical instruments. In the NeXUS STM, XUV pulses will illuminate the tunnel junction, thus allowing access to element-specific core level transitions and ultrafast time resolution. As the energy of the XUV is tuned above a core transition of a particular element, electrons will be emitted from the sample and locally collected by a customized STM tip. The ability to perform optical pump-optical probe, as well as optical pump-XUV probe, experiments adds capability for ultra-fast, atomic scale, measurements of carrier dynamics at surfaces and interfaces. The STM operates in ultra-high vacuum and utilizes a closed cycle cryocooler which allows for uninterrupted measurements of atomically clean surfaces at cryogenic (11 K) temperatures. The instrument was installed in July 2021 and is fully operational, allowing the initial characterization measurements shown here, as well as the development of remote operation for users.

(top) Image of the STM in the NeXUS laser lab. The STM chamber is on a concrete slab for vibration stabilization, and the enclosure for the closed cycle cooler is to the left of the chamber. The optical table can be seen in the background behind the chamber. (right) Image taken by the STM of the Au(111) surface at 11 K showing the characteristic herringbone reconstruction, as well as a single atomic step. (bottom left) The corrugation of the herringbone pattern can be seen in the line trace and indicates a tip stability of < 2 pm. (bottom center) STM temperature during an initial cool down to a base temperature of 11 K. The inset shows temperature stability better than 350 mK  over a week with no user-added cryogens.

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Have a great Fall!
-The NeXUS Team