Spring 2024 NeXUS News
System Spotlight – Liquid Sheet Apparatus for Static and Transient XAS
When coupled to the XAS end station, the liquid sheet apparatus will provide users with the opportunity to perform static and transient (EUV to soft X-ray) absorbance measurements in the solution-phase. EUV spectroscopy provides intrinsic specificity of the element, spin-state, oxidation-state, and coordination environment of the target molecule. The liquid sheet apparatus enables solution-phase studies and offers the possibility of developing a molecular level understanding of processes with relevance to biology, energy conservation and conversion, and catalysis. Solution-phase studies will improve our understanding of fundamental processes (such as conical intersections) for systems that are naturally in solution. In addition, this approach can guide research and development efforts to develop more efficient molecular systems for applications such as photocatalysis or phototherapy.
The primary hurdle to solution-phase EUV measurements is the attenuation of the probe beam by the solvent. A solution to this, employing an ultrathin liquid sheet between 16 and 1000 nm, was first demonstrated by a team at LCLS (Koralek, et al., Nat. Commun., 9, 1353 (2018)). The NeXUS liquid sheet apparatus is based on this LCLS implementation and the implementation by Louis DiMauro’s group at Ohio State.
NeXUS has been building their liquid sheet apparatus. A recent test generated and imaged a liquid sheet as shown in the photograph below. NeXUS captured preliminary length and width measurements and is implementing a thickness characterization system. Once completed, the liquid sheet apparatus can be exchanged for the solid-state sample chamber in the NeXUS XAS/XRS beamline. This beamline provides probe pulses from 30 to 300 eV (covering the 3d transition metal M2,3 edge as well as O & S L-edge and C K-edge) and pump pulses between 330 to 2000 nm, allowing for dynamics studies with resolution <65 fs and time scales up to ~1 ns.
Staff Spotlight – Jacob Byron, Laboratory Operations
Jacob Byron joined Ohio State in January 2024 as the NeXUS Facility’s Laboratory Research Operations Analyst. Jacob earned his BS in Zoology from Minnesota State University. He worked at the Minnesota Zoo, the Virginia Aquarium, and the Columbus Zoo as a life support systems engineer, designing and building aquatic habitats. You can see his latest project, the weedy sea dragon exhibit, at the Columbus Zoo. 
Jacob will bring his knowledge and experience with mechanical maintenance, PLC automation, and system design and engineering to the NeXUS team. He is excited to apply his skills to new systems and support the researchers that come to use the facility.
Year-End 2023 NeXUS News
The NeXUS Laser Has Arrived!
The NeXUS Facility development project took a giant leap forward in October with the arrival of the NeXUS laser. A team from Active Fiber Systems (the laser manufacturer based in Jena, Germany) spent a week in the lab assisting the NeXUS team with chamber placement, installation, and testing to ensure all components arrived in good working order. Additional AFS teams will travel to Columbus over the next several weeks to help get all of the laser capabilities up and running and to train the NeXUS team on laser operation. We’re excited to see our vision finally coming to life!
System Spotlight – Laser Induced Electron Diffraction (LIED)
The LIED/ATTO end station at NeXUS will provide an opportunity for users to perform Laser Induced Electron Diffraction (LIED) as well as ATTO experiments such as Reconstruction of Attosecond Beating By Interference of Two-photon Transitions (RABBITT) and streaking. LIED enables probing molecular dynamics with sub-angstrom and sub-femtosecond spatial and temporal resolution using re-scattering physics. In LIED experiments, it is required to collect a large number of data to obtain spectra with reasonable signal to noise ratio which can be tedious when operated at a low repetition rate. The NeXUS laser will enable us to run such experiments with 100 kHz repetition rate and therefore accelerate data acquisition procedure. In addition, with high repetition rate, it will be feasible to do pump-probe LIED which has not been investigated before. As for the ATTO mode, the end-station has the capability of studying attosecond electron dynamics such as correlated electron dynamics, molecular charge migration and ultrafast photoemission probed at 100 kHz sampling rate.
A schematic of the apparatus used to conduct such experiments is shown in the top left figure. It is a Symmetric Double Time-of Flight (SD-TOF) which can operate in two modes: (1) electron detection on both sides, (2) having one side for electron detection and the other side for ion detection. For detecting electrons, the spectrometer functions in field-free mode since electric fields can affect the kinetic energy of the electrons and the magnetic field can modify their angular distribution. In order to shield electrons from stray electric fields, the field plates are built from molybdenum and uniformly coated by graphite which minimizes the patch effect. Three Mu-metal cylinders are used to cover the spectrometer (including the interaction region and the flight tubes) and isolate it from Earth’s magnetic field which can deviate flying electrons and adversely affect the resolution. In ion mode, it is a Time of Flight (ToF) mass spectrometer in which a non-uniform electric field is applied to the field plates which accelerates the ions towards the detector. The charged particles are detected using fast timing Multi Channel Plate (MCP) chevron detectors connected to a high speed digitizer.
Staff Spotlight – Seth Shields, Applied Research Scientist
Dr. Seth Shields is an applied research scientist working on the scanning tunneling microscopy end station and micro-focusing beamline at the NeXUS facility. He double majored in physics and German at Washington University in St. Louis before earning his PhD in physics from Ohio State under the supervision of Professor Jay Gupta. His research focused on low temperature scanning tunneling microscopy studies of copper oxidation, and the interaction of oxidized copper surfaces with adsorbed CO2. During his time as a student, he also supported the development and installation of the STM end station and micro-focusing beamline. Following the completion of his PhD in 2023, he stayed at NeXUS as a postdoctoral researcher, and recently transitioned to an applied research scientist staff position. Seth looks forward to supporting user experiments utilizing the NeXUS STM beamline and end station and would be glad to discuss potential proposal ideas.
Spring 2023 NeXUS News
Lab Progress Update
The NeXUS lab is advancing by leaps and bounds! Accomplishments in recent months include:
- Custom-built vacuum chambers received, installed, and verified
- STM beamline and LIED subsystems ready for verification testing
- Component racks built around beamline tables
- First test of potential integrated software solution
- Manufacturer site visit for hands-on demonstration of laser in progress
We have also begun to accept user proposals on a preliminary basis for validation experiments utilizing the capabilities of the stand-alone STM and ARPES end stations. Many experiments can be completed remotely with samples shipped to the NeXUS Facility. Visit our NeXUS Users page here to learn more about these opportunities. We encourage you to reach out to a NeXUS Faculty member to discuss your experimental idea and the evolving capabilities of our facility. Get to know our faculty and their areas of expertise here.
The XAS/XRS beamline and the roll-up XAS end station (left)
ARPES vacuum chamber with optomechanics inside
Beamline control electronics
Preparing for laser delivery
STM beamline chambers assembled and under vacuum
Check out our latest time lapse video and watch as we move closer to first light:
X-Lites Network Brings Focus to Extreme Light Science
X-lites – the Extreme Light in Intensity, Time and Space Network – is an NSF-sponsored international network of researchers and facilities from around the world. The goal of this network of networks is to enhance collaboration, knowledge sharing, and engagement among these new extreme light facilities and by doing so accelerate research. The network hosts a variety of online and in-person events as well as a newsletter to promote these goals.
Find a calendar of events, subscribe to the newsletter, and learn more about the X-Lites Network at its website: Click here
Meet the NeXUS Staff
Karen Keller, Business Operations
Karen Keller joined Ohio State in October 2021 as the NeXUS Facility’s Business Operations Specialist. Karen earned her MS in environmental horticulture from the University of Florida and has worked as a biological scientist for UF’s Mid-Florida Research and Education Center and for the USDA Agricultural Research Service.
Prior to joining NeXUS, Karen was the administrative director for a nonprofit organization for 10 years. In this role, Karen cultivated skills in supporting teams, fiscal management, and grant writing and development. Karen looks forward to supporting the NeXUS Facility as it transitions into a fully operational user facility, and to meeting scientists from around the world who work on the cutting edge of technological advancement and world-changing science.
System Spotlight
Time- and Angle-resolved Photoelectron Spectroscopy (trARPES)
Description of NEXUS trARPES
Time- and angle-resolved photoelectron spectroscopy (trARPES) at NEXUS provides users with a powerful tool to study the band structures of solid state samples, as well as the related carrier dynamics. In trARPES experiments, the pump pulse (usually infrared or visible) first generates a non-equilibrium distribution of carriers in the sample. After an appropriate time delay, the probe pulse (extreme ultraviolet with photon energy > 6 eV) arrives at the sample and ejects the electrons out of the sample. By collecting and analyzing the electron and momentum distribution of ejected electrons, one obtains information about the dynamics of the band structures in the sample. At NEXUS, the trARPES is equipped with a state-of-the-art Specs KREIOS 150 MM end station, which has simultaneous spatial-, momentum- and energy-resolution.
trARPES Beamline Construction
During the past several months, our team has been constructing the beamline for the time- and angle-resolved photoelectron spectroscopy (trARPES) at NeXUS. So far, the high-harmonic generation (HHG) chamber, the monochromator chamber and the final focusing chamber have been placed onto the optics table. Among them, the monochromator chamber and the final focusing chamber have passed the vacuum test, and the vacuum test for HHG chamber is expected to be finished this month. Beyond the installation of the chambers, we are also actively working on building the beamline between the monochromator and the final focusing chamber. All the chambers in the trARPES beamline will be interconnected and pumped down in 4-5 weeks. Once the beamline is finished, it will be able to deliver monochromatic laser pulses in the 10-100 eV range for ARPES experiments.
(Left) Schematic drawing of trARPES experiment and Specs KREIOS 150 MM endstation. (Top right) CAD drawing of the NEXUS trARPES beamlines. (Bottom right) Photograph of the trARPES optics table, showing recent progress in beamline construction.
Fall 2022 NeXUS News
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
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.