Physics Commons^™

The Influence Of The Substrate On The Functionality Of Spin Crossover Molecular Materials, Saeed Yazdani, Jared Phillips, Thilini K. Ekanayaka, Ruihua Cheng, Peter A. Dowben

Department of Physics and Astronomy: Faculty Publications

Spin crossover complexes are a route toward designing molecular devices with a facile readout due to the change in conductance that accompanies the change in spin state. Because substrate effects are important for any molecular device, there are increased efforts to characterize the influence of the substrate on the spin state transition. Several classes of spin crossover molecules deposited on different types of surface, including metallic and non-metallic substrates, are comprehensively reviewed here. While some non-metallic substrates like graphite seem to be promising from experimental measurements, theoretical and experimental studies indicate that 2D semiconductor surfaces will have minimum interaction with …

Stabilizing Polar Phases In Binary Metal Oxides By Hole Doping, Tengfei Cao, Guodong Ren, Ding-Fu Shao, Evgeny Y. Tsymbal, Rohan Mishra

Department of Physics and Astronomy: Faculty Publications

The recent observation of ferroelectricity in the metastable phases of binary metal oxides, such as HfO₂, ZrO₂, Hf_0.5Zr_0.5O₂, and Ga₂O₃, has garnered a lot of attention. These metastable ferroelectric phases are typically stabilized using epitaxial strain, alloying, or defect engineering. Here, we propose that hole doping plays a key role in the stabilization of polar phases in binary metal oxides. Using first-principles density-functional-theory calculations, we show that holes in these oxides mainly occupy one of the two oxygen sublattices. This hole localization, which is more pronounced …

The Spin Polarization Of Palladium On Magneto-Electric Cr2O3, Takashi Komesu, Will Echtenkamp,, Christian H. Binek, Peter A. Dowben

Department of Physics and Astronomy: Faculty Publications

While induced spin polarization of a palladium (Pd) overlayer on antiferromagnetic and magneto-electric Cr₂O₃(0001) is possible because of the boundary polarization at the Cr₂O₃(0001), in the single domain state, the Pd thin film appears to be ferromagnetic on its own, likely as a result of strain. In the conduction band, we find the experimental evidence of ferromagnetic spin polarized in Pd thin films on a Cr₂O₃(0001) single crystal, especially in the thin limit, Pd thickness of around 1–4 nm. Indeed there is significant spin polarization in 10 Å …

E6 Models In Light Of Precision MW Measurements, Vernon Barger, Cash Hauptmann, Peisi Huang, Wai-Yee Keung

Department of Physics and Astronomy: Faculty Publications

We propose a solution to the recent W mass measurement by embedding the Standard Model within E₆ models. The presence of a new U(1) group shifts the W boson mass at the tree level and introduces a new gauge boson Z' which has been searched for at collider experiments. In this article, we identify the parameter space that explains the new W mass measurement and is consistent with current experimental Z' searches. As U(1) extensions can be accommodated in supersymmetric models, we also consider the supersymmetric scenario of E₆ models, and show that a 125 GeV …

Test Beam Performance Of A Cbc3-Based Mini-Module For The Phase-2 Cms Outer Tracker Before And After Neutron Irradiation, Cms Collaboration

Department of Physics and Astronomy: Faculty Publications

The Large Hadron Collider (LHC) at CERN will undergo major upgrades to increase the instantaneous luminosity up to 5–7.5 × 10³⁴ cm^-2s^-1. This High Luminosity upgrade of the LHC (HL-LHC) will deliver a total of 3000–4000 fb^-1 of proton-proton collisions at a center-of-mass energy of 13–14 TeV. To cope with these challenging environmental conditions, the strip tracker of the CMS experiment will be upgraded using modules with two closely-spaced silicon sensors to provide information to include tracking in the Level-1 trigger selection. This paper describes the performance, in a test beam experiment, of the …

A Method To Measure Positron Beam Polarization Using Optically Polarized Atoms, Joshua Joshua Machacek, Sean Hodgman, Stephen Buckman, T. J. Gay

Department of Physics and Astronomy: Faculty Publications

We outline an experimental technique for measuring the degree of polarization of a positron beam using an optically pumped, spin-polarized Rb target. The technique is based on the production and measurement of the ortho- and para-positronium fractions through positron collisions with the Rb atoms as a function of their polarization. Using realistic estimates for the cross sections and experimental parameters involved, we estimate that a polarization measurement with an uncertainty of 3% of the measured value can be achieved in an hour

Diffractive Imaging Of Laser Induced Molecular Reactions With Kiloelectron-Volt Ultrafast Electron Diffraction, Yanwei Xiong

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Capturing the structural changes during a molecular reaction with ultrafast electron diffraction (UED) requires a high spatiotemporal resolution and sufficiently high signal-to-noise to record the signals with high fidelity. In this dissertation, I have focused on the development of a tabletop gas phase keV-UED setup with a femtosecond temporal resolution. A DC electron gun was employed to generate electron pulses with a high repetition rate of 5 kHz. The space charge effect in the electron pulse was ameliorated by compressing the 90 keV electron pulse longitudinally with a time varying electric field in an RF cavity. The velocity mismatch between …

Interface-Engineered Ferroelectricity Of Epitaxial Hf0.5Zr0.5O2 Thin Films, Shu Shi, Haolong Xi, Tengfei Cao, Weinan Lin, Zhongran Liu, Jiangzhen Niu, Da Lan, Chenghang Zhou, Jing Cao, Hanxin Su, Tieyang Zhao, Ping Yang, Yao Zhu, Xiaobing Yan, Evgeny Y. Tsymbal, He Tian, Jingsheng Chen

Department of Physics and Astronomy: Faculty Publications

Ferroelectric hafnia-based thin films have attracted intense attention due to their compatibility with complementary metal-oxide-semiconductor technology. However, the ferroelectric orthorhombic phase is thermodynamically metastable. Various efforts have been made to stabilize the ferroelectric orthorhombic phase of hafnia-based films such as controlling the growth kinetics and mechanical confinement. Here, we demonstrate a key interface engineering strategy to stabilize and enhance the ferroelectric orthorhombic phase of the Hf_0.5Zr_0.5O₂ thin film by deliberately controlling the termination of the bottom La_0.67Sr_0.33MnO₃ layer. We find that the Hf_0.5Zr_0.5O₂ films on …

Prominent Size Effects Without A Depolarization Field Observed In Ultrathin Ferroelectric Oxide Membranes, Haoying Sun, Jiahui Gu, Yongqiang Li, Tula R. Paudel, Di Liu, Jierong Wang, Yipeng Zang, Chengyi Gu, Jiangfeng Yang, Wenjie Sun, Zhengbin Gu, Evgeny Y. Tsymbal, Junming Liu, Houbing Huang, Di Wu, Yuefeng Nie

Department of Physics and Astronomy: Faculty Publications

The increasing miniaturization of electronics requires a better understanding of material properties at the nanoscale. Many studies have shown that there is a ferroelectric size limit in oxides, below which the ferroelectricity will be strongly suppressed due to the depolarization field, and whether such a limit still exists in the absence of the depolarization field remains unclear. Here, by applying uniaxial strain, we obtain pure in-plane polarized ferroelectricity in ultrathin SrTiO₃ membranes, providing a clean system with high tunability to explore ferroelectric size effects especially the thickness-dependent ferroelectric instability with no depolarization field. Surprisingly, the domain size, ferroelectric transition …

Azimuthal Correlations In Z +Jets Events In Proton–Proton Collisions At √S = 13tev, Cms Collaboration

Department of Physics and Astronomy: Faculty Publications

The production of Z bosons associated with jets is measured in pp collisions at √ s = 13 TeV with data recorded with the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3 fb⁻¹. The multiplicity of jets with transverse momentum p_T > 30 GeV is measured for different regions of the Z boson’s p_T(Z ), from lower than 10 GeV to higher than 100 GeV. The azimuthal correlation Δφ between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions …

Search For The Higgs Boson Decay To A Pair Of Electrons In Proton-Proton Collisions At √S = 13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search is presented for the Higgs boson decay to a pair of electrons (e⁺e⁻) in proton-proton collisions at √ s = 13 TeV. The data set was collected with the CMS experiment at the LHC between 2016 and 2018, corresponding to an integrated luminosity of 138 fb⁻¹. The analysis uses event categories targeting Higgs boson production via gluon fusion and vector boson fusion. The observed upper limit on the Higgs boson branching fraction to an electron pair is 3.0 × 10⁻⁴ (3.0 × 10⁻⁴ expected) at the 95% confidence level, which …

Erratum: Measurement Of Prompt And Nonprompt Charmonium Suppression In Pbpb Collisions At 5.02 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

In Fig. 3, the y axis titles were mistakenly written showing a single-differential cross section in either dimuon p_T or rapidity, when in fact the cross section is normalized by both the p_T and rapidity ranges used for a given measurement point. The corrected version is shown in the new Fig. 3 provided below.

Effects Of Intermixing And Oxygen Vacancies On A Two-Dimensional Electron Gas At The Polar (Tbsco3/Ktao) (001) Interface, Bhubnesh Lama, Evgeny Y. Tsymbal, Tula R. Paudel

Department of Physics and Astronomy: Faculty Publications

3d-5d perovskite oxides, ABO₃ (where A and B are 3d or 5d elements), form polar surfaces in the (001)- stacked thin films. As a result, the polar-polar (001) interface between two ABO₃ insulators could create polar discontinuity potentially producing a two-dimensional electron gas of higher density and stronger spatial localization compared to the widely studied polar-nonpolar oxide interfaces, such as (001) LaAlO₃/SrTiO₃. Here, as a model system, we explore the interface between polar (001) TbScO₃ and polar (001) KTaO₃ using first-principles density functional theory.We find that the …

Chiral Photocurrent In A Quasi-1d Tis3 (001) Phototransistor, Simeon J. Gilbert, Mingxing Li, Jia-Shiang Chen, Hemian Yi, Alexey Lipatov, Jose Avila, Alexander Sinitskii, Maria C. Asensio, Peter A. Dowben, Andrew J. Yost

Department of Physics and Astronomy: Faculty Publications

The presence of in-plane chiral effects, hence spin–orbit coupling, is evident in the changes in the photocurrent produced in a TiS₃(001) field-effect phototransistor with left versus right circularly polarized light. The direction of the photocurrent is protected by the presence of strong spin–orbit coupling and the anisotropy of the band structure as indicated in NanoARPES measurements. Dark electronic transport measurements indicate that TiS₃ is n-type and has an electron mobility in the range of 1–6 cm²V⁻¹s⁻¹. I–V measurements under laser illumination indicate the photocurrent exhibits a bias directionality dependence, reminiscent of …

Domain‑Wall Magnetoelectric Coupling In Multiferroic Hexagonal Ybfeo3 Films, Xin Li, Yu Yun, Arashdeep Singh Thind, Yuewei Yin, Qiang Li, Wenbin Wang, Alpha T. N’Diaye, Corbyn Mellinger, Xuanyuan Jiang, Rohan Mishra, Xiaoshan S. Xu

Department of Physics and Astronomy: Faculty Publications

Electrical modulation of magnetic states in single-phase multiferroic materials, using domain-wall magnetoelectric (ME) coupling, can be enhanced substantially by controlling the population density of the ferroelectric (FE) domain walls during polarization switching. In this work, we investigate the domain-wall ME coupling in multiferroic h-YbFeO₃ thin films, in which the FE domain walls induce clamped antiferromagnetic (AFM) domain walls with reduced magnetization magnitude. Simulation according to the phenomenological theory indicates that the domain-wall ME effect is dramatically enhanced when the separation between the FE domain walls shrinks below the characteristic width of the clamped AFM domain walls during the ferroelectric …

Antiproton Collisions With Excited Positronium, M. Charlton, H. B. Ambalampitiya, Ilya I. Fabrikant, I. Kalinkin, D. V. Fursa, A. S. Kadyrov, I. Bray

Department of Physics and Astronomy: Faculty Publications

We present results of calculations of several processes resulting from positronium (Ps) collisions with antiprotons: antihydrogen formation, Ps breakup, and n_Ps-changing collisions. Calculations utilize the quantum convergent close-coupling (CCC) method and the classical trajectory Monte Carlo (CTMC) method. We identify a region of Ps principal quantum numbers n_Ps and Ps energies where the classical description is valid and where the CCC calculations become computationally too expensive. This allows us to present the most complete and reliable set of cross sections in a broad range of n_Ps and initial orbital momentum quantum numbers lPs which are necessary …

In-Plane Ferroelectric Tunnel Junctions Based On 2d Α-In2Se3/ Semiconductor Heterostructures, Zifang Liu, Pengfei Hou, Lizhong Sun, Evgeny Y. Tsymbal, Jie Jiang, Qiong Yang

Department of Physics and Astronomy: Faculty Publications

Ferroelectric tunnel junctions (FTJs) have great potential for application in high-density non-volatile memories. Recently, α-In₂Se₃ was found to exhibit robust in-plane and out-of-plane ferroelectric polarizations at a monolayer thickness, which is ideal to serve as a ferroelectric component in miniaturized electronic devices. In this work, we design two-dimensional van der Waals heterostructures composed of an α-In₂Se₃ ferroelectric and a hexagonal IV–VI semiconductor and propose an in-plane FTJ based on these heterostructures. Our first-principles calculations show that the electronic band structure of the designed heterostructures can be switched between insulating and metallic states by ferroelectric …

Pressure-Induced Charge Orders And Their Postulated Coupling To Magnetism In Hexagonal Multiferroic Lufe2O4, Fengliang Liu, Yiqing Hao, Jinyang Ni, Yongsheng Zhao, Dongzhou Zhang, Gilberto Fabbris, Daniel Haskel, Shaobo Cheng, Xiaoshan Xu, Lifeng Yin, Hongjun Xiang, Jun Zhao, Xujie Lü, Wenbin Wang, Jian Shen, Wenge Yang

Department of Physics and Astronomy: Faculty Publications

Hexagonal LuFe₂O₄ is a promising charge order (CO) driven multiferroic material with high charge and spin-ordering temperatures. The coexisting charge and spin orders on Fe³⁺/Fe²⁺ sites result in magnetoelectric behaviors, but the coupling mechanism between the charge and spin orders remains elusive. Here, by tuning external pressure, we reveal three charge-ordered phases with suggested correlation to magnetic orders in LuFe₂O₄: (i) a centrosymmetric incommensurate three-dimensional CO with ferrimagnetism, (ii) a non-centrosymmetric incommensurate quasi-two-dimensional CO with ferrimagnetism, and (iii) a centrosymmetric commensurate CO with antiferromagnetism. Experimental in situ single-crystal X-ray diffraction …

New Features In Landyne 5 - A Software Suite For Materials Characterization And Crystallography By Transmission Electron Microscopy, Xing-Zhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

Landyne software suite (version 5) includes fifteen standalone computer programs for materials characterization and crystallography by transmission electron microscopy [1]. A launcher interface is provided for users to access all components conveniently. The purpose of this software suite is twofold: i) as research tools to analyze experimental results, ii) as teaching tools to explore the varieties of electron diffraction methods and crystallographic image processing principles.

The Landyne suite previously included: PTable, an interactive periodic table of elements; SVAT, a structural visual and analytical tool; SAED and PCED, simulation and analysis of electron diffraction (spot and ring) patterns; QSAED and QPCED, …

Structural, Electronic, And Magnetic Properties Of Cofevge-Based Compounds: Experiment And Theory, Parashu Kharel, Zachary Lehmann, Gavin Baker, Lukas Stuelke, Shah R. Valloppilly, Paul M. Shand, Pavel V. Lukashev

Nebraska Center for Materials and Nanoscience: Faculty Publications

We have carried out a combined theoretical and experimental investigation of both stoichiometric and nonstoichiometric CoFeVGe alloys. In particular, we have investigated CoFeVGe, Co_1.25Fe_0.75VGe, Co_0.75Fe_1.25VGe, and CoFe_0.75VGe bulk alloys. Our first principles calculations suggest that all four alloys show ferromagnetic order, where CoFeVGe, Co_1.25Fe_0.75VGe, and Co_0.75Fe_1.25VGe are highly spin polarized with spin polarization values of over 80%. However, the spin polarization value of CoFe_0.75VGe is only about 60%. We have synthesized all four samples using arc melting and high-vacuum annealing …

Tem Studies Of A New Modulated Structure In Mn2Rusn Alloy And Intermetallic Phases In Fe3+XCo3–XTi2 (X = 0, 1, 2, 3) Alloys, Xing-Zhong Li, Shah R. Valloppilly

Nebraska Center for Materials and Nanoscience: Faculty Publications

Heusler compounds are a remarkable class of intermetallic materials with wide-ranging and tunable properties. The Mn₂RuSn Heusler compound was reported as an L2₁B-type cubic phase, a = 0.62195 nm, distinguishing from the original L2₁ structure (or L2₁A-type). The L2₁B-type structure is a disordered variant of the inverse Heusler structure, XA-type (Prototype-CuHg₂Ti, space group No. 216, F4–3m).

In our recent work [1], we observed a new modulated structure derived from the XA-type structure and its orthogonal domains in the Mn₂RuSn Heusler alloy. The structural characterization was carried out …

Entropy-Driven Structural Transition From Tetragonal To Cubic Phase: High Thermoelectric Performance Of Cucdinse3 Compound, Tingting Luo, Yihao Hu, Shi Liu, Fanjie Xia, Junhao Qiu, Haoyang Peng, Keke Liu, Quansheng Guo, Xingzhong Li, Dongwang Yang, Xianli Su, Jinsong Wu, Xinfeng Tang

Nebraska Center for Materials and Nanoscience: Faculty Publications

Cu based chalcopyrite is an important class of thermoelectric materials with excellent electronic properties, however, the thermal conductivity is relatively high due to the simple tetragonal structure with highly ordered configuration on cation sites, limiting the thermoelectric performance. Herein, we realize that the modulation of entropy via alloying CdSe achieves the structural transition from tetragonal structure with ordered configuration on cations sites in CuInSe₂ compound to cubic CuCdInSe₃. CuCdInSe₃ crystallizes in a zinc blende (ZnS) structure where Cu, Cd and In cations randomly occupy the Zn site with the occupancy fraction 1/3. This entropy driven order-disorder …

Proton Reconstruction With The Cms-Totem Precision Proton Spectrometer, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb⁻¹ in proton-proton (pp) collisions at the LHC at 13 TeV (Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider.

Switchable Anomalous Hall Effects In Polar-Stacked 2d Antiferromagnet Mnbi2Te4, Tengfei Cao, Ding-Fu Shao, Kai Huang, Gautam Gurung, Evgeny Y. Tsymbal

Department of Physics and Astronomy: Faculty Publications

Van der Waals (vdW) assembly allows controlling symmetry of two-dimensional (2D) materials that determines their physical properties. Especially interesting is the recently demonstrated breaking inversion symmetry by polar layer stacking to realize novel electronic, magnetic, and transport properties of 2D vdW materials switchable by induced electric polarization. Here, based on symmetry analyses and density-functional calculations, we explore the emergence of the anomalous Hall effect (AHE) in antiferromagnetic MnBi2Te4 films assembled by polar layer stacking. We demonstrate that breaking 𝑃̂ 𝑇̂ symmetry in an MnBi₂Te₄ bilayer makes this 2D material magnetoelectric and produces a spontaneous AHE switchable by …

Anisotropic Optical And Magnetic Response In Self-Assembled Tin-Cofe2 Nanocomposites, Jiawei Song, Di Zhang, Ping Lu, Haohan Wang, X. S. Xu, Melissa L. Meyerson, Samantha G. Rosenberg, Julia Deitz, Juncheng Liu, Xuejing Wang, Xinghang Zhang

Department of Physics and Astronomy: Faculty Publications

Transition metal nitrides (e.g., TiN) have shown tremendous promise in optical metamaterials for nanophotonic devices due to their plasmonic properties comparable to noble metals and superior high temperature stability. Vertically aligned nanocomposites (VANs) offer a great platform for combining two dissimilar functional materials with a one-step deposition technique toward multifunctionality integration and strong structural/property anisotropy. Here we report a two-phase nanocomposite design combining ferromagnetic CoFe₂ nanosheets in the plasmonic TiN matrix as a new hybrid plasmonic metamaterial. The hybrid metamaterials exhibit obvious anisotropic optical and magnetic responses, as well as a pronounced magneto-optical coupling response evidenced by MOKE measurement, …

Direct Observation Of The Magnetic Anisotropy Of An Fe (Ii) Spin Crossover Molecular Thin Film, Ashley S. Dale, Saeed Yazdani, Thilini K. Ekanayaka, Esha Mishra, Yuchen Hu, Peter A. Dowben, John W. Freeland, Jian Zhang, Ruihua Cheng

Department of Physics and Astronomy: Faculty Publications

Spin crossover molecules are a promising candidate for molecular spintronics that aim for ultrafast and low-power devices for data storage and magnetic and information sensing. The rapid spin state transition is best controlled by non-thermal methods including magnetic field. Unfortunately, the magnetic field normally required to switch the spin state is normally high (~30 T), which calls for better understanding of the fundamental mechanism. In this work, we provide clear evidence of magnetic anisotropy in the local orbital moment of a molecular thin film based on spin crossover complex [Fe(H₂B(pz)₂)₂(bipy)] (pz = pyrazol−1−yl, bipy …

Interface-Tuning Of Ferroelectricity And Quadruple-Well State In Cuinp2S6 Via Ferroelectric Oxide, Kun Wang, Du Li, Jia Wang, Yifei Hao, Hailey Anderson, Li Yang, Xia Hong

Department of Physics and Astronomy: Faculty Publications

Ferroelectric van der Waals CuInP₂S₆ possesses intriguing quadruple-well states and negative piezoelectricity. Its technological implementation has been impeded by the relatively low Curie temperature (bulk T_C ~42 °C) and the lack of precise domain control. Here we show that CuInP₂S₆ can be immune to the finite size effect and exhibits enhanced ferroelectricity, piezoelectricity, and polar alignment in the ultrathin limit when interfaced with ferroelectric oxide PbZr_0.2Ti_0.8O₃ films. Piezoresponse force microscopy studies reveal that the polar domains in thin CuInP₂S₆ fully conform to those of underlying …

Nitrogen-Vacancy Magnetometry Of Individual Fe-Triazole Spin Crossover Nanorods, Suvechhya Lamichhane, Kayleigh A. Mcelveen, Adam Erickson, Ilja Fescenko, Shuo Sun, Rupak Timalsina, Yinsheng Guo, Sy_Hwang Liou, Rebecca Lai, Abdelghani Laraoui

Department of Physics and Astronomy: Faculty Publications

[Fe(Htrz)₂(trz)](BF₄) (Fe-triazole) spin crossover molecules show thermal, electrical, and optical switching between high spin (HS) and low spin (LS) states, making them promising candidates for molecular spintronics. The LS and HS transitions originate from the electronic configurations of Fe(II) and are considered to be diamagnetic and paramagnetic respectively. The Fe(II) LS state has six paired electrons in the ground states with no interaction with the magnetic field and a diamagnetic behavior is usually observed. While the bulk magnetic properties of Fe-triazole compounds are widely studied by standard magnetometry techniques their magnetic properties at the individual level …

Femtosecond Electronic And Hydrogen Structural Dynamics In Ammonia Imaged With Ultrafast Electron Diffraction, Elio G. Champenois, Nanna H. List, Matthew Ware, Mathew Britton, Philip H. Bucksbaum, Xinxin Cheng, Martin Centurion, James P. Cryan, Ruaridh Forbes, Ian Gabalski, Kareem Hegazy, Matthias C. Hoffmann, Andrew J. Howard, Fuhao Ji, Ming-Fu Lin, J. Pedro F. Nunes, Xiaozhe Shen, Jie Yang, Xijie Wang, Todd J. Martinez, Thomas J. A. Wolf

Department of Physics and Astronomy: Faculty Publications

Directly imaging structural dynamics involving hydrogen atoms by ultrafast diffraction methods is complicated by their low scattering cross sections. Here we demonstrate that megaelectronvolt ultrafast electron diffraction is sufficiently sensitive to follow hydrogen dynamics in isolated molecules. In a study of the photodissociation of gas phase ammonia, we simultaneously observe signatures of the nuclear and corresponding electronic structure changes resulting from the dissociation dynamics in the time-dependent diffraction. Both assignments are confirmed by ab initio simulations of the photochemical dynamics and the resulting diffraction observable. While the temporal resolution of the experiment is insufficient to resolve the dissociation in time, …

Coordination Chemistry Of Uranyl Ions With Surface-Immobilized Peptides: An Xps Study, Esha Mishra, Cody M. Schultz, Rebecca Lai, Peter A. Dowben

Department of Physics and Astronomy: Faculty Publications

The coordination chemistry of uranyl ions with surface immobilized peptides was studied using X-ray photoemission spectroscopy (XPS). All the peptides in the study were modified using a six-carbon alkanethiol as a linker on a gold substrate with methylene blue as the redox label. The X-ray photoemission spectra reveal that each modified peptide interacts differently with the uranyl ion. For all the modified peptides, the XPS spectra were taken in both the absence and presence of the uranium, and their comparison reveals that the interaction depends on the chemical group present in the peptides. The XPS results show that, among all …