In spectroscopy experiments, a sample is illuminated with light and the various product particles (electrons, ions, or fluorescent photons) are detected and analyzed.The unifying feature is that some "property" of a material is measured as the x-ray (photon) energy is swept though a range of values. At the most basic level, one measures the absorption, transmission, or reflectivity of a sample as a function of photon energy.
Probes that use the vacuum ultraviolet (VUV) region of the spectrum (10–100 eV) are very well matched to the elucidation of bonding in solids, surfaces, and molecules; to the investigation of electron–electron correlations in solids, atoms, and ions; and to the study of reaction pathways in chemical dynamics. At the lowest end of this energy range (below 1 eV) we have infrared, far-infrared, and terahertz spectroscopies, which are well matched to vibrational modes and other modes of excitation.
Soft x-ray spectroscopies employ the excitation of electrons in relatively shallow core levels (100–2000 eV) to probe the electronic structure of various kinds of matter. Elemental specificity is the watchword for this kind of spectroscopy. Each element has its own set of core levels that occur at characteristic energies. The photon-energy tunability of synchrotron radiation is essential.
Hard x-ray spectroscopy is applied in a wide variety of scientific disciplines (physics, chemistry, life sciences, and geology) to investigate geometric and electronic structure. The method is element-, oxidation-state-, and symmetry-specific. It is a primary tool in the characterization of new and promising materials. It is also used in the elucidation of dilute chemical species of environmental concern.
Selected Spectroscopy Highlights
Flipping Photoelectron Spins in Topological Insulators
Studies Bolster Promise of Topological Insulators
A New Route to Nanoscale Conducting Channels in Insulating Oxides
A Better Anode Design to Improve Lithium-Ion Batteries
A Microscopic Double-Slit Experiment
Direct Kinetic Measurements of a Criegee Intermediate
Two Phase Transitions Make a High-Temperature Superconductor
Large Magnetization at Carbon Surfaces
Regarding Confinement Resonances
AP-XPS Measures Active MIEC Oxides in Action
Heterogeneous Morphology Found in Organic Solar Cells
Probing Strain-Induced Changes in Electronic Structure with XMCD
Superconducting Topological Insulators
Molecular Measurements of the Deep-Sea Oil Plume in the Gulf of Mexico
Platinum Nanoclusters Out-Perform Single Crystals
ALS Reveals New State of Matter
Compositional Variation Within Hybrid Nanostructures
First Observation of Plasmarons in Graphene
Site-Selective Ionization in Nanoclusters Affects Subsequent Fragmentation
Biomimetic Dye Molecules for Solar Cells
Electron Correlation in Iron-Based Superconductors
Harnessing the Bacterial Power of Nanomagnets
Bilayer Graphene Gets a Bandgap
Towards Heavy Fermions in Europium Intermetallic Compounds
Observation of a Macroscopically Quantum-Entangled Insulator
Reaction-Driven Restructuring of Bimetallic Nanoparticle Catalysts
Dirac Charge Dynamcs in Graphene by Infrared Spectroscopy
Isotope and Temperature Effects in Liquid Water Probed by Soft X Rays