Superfluid helium-4 is the superfluid form of helium-4,an isotope of the element helium. A superfluid is a state of matter in which matter behaves like a fluid with zero viscosity. The substance,which resembles other liquids such as helium I,flows without friction past any surface,which allows it to continue to circulate over obstructions and through pores in containers which hold it,subject only to its own inertia.
Electron energy loss spectroscopy (EELS) is a form of electron microscopy in which a material is exposed to a beam of electrons with a known,narrow range of kinetic energies. Some of the electrons will undergo inelastic scattering,which means that they lose energy and have their paths slightly and randomly deflected. The amount of energy loss can be measured via an electron spectrometer and interpreted in terms of what caused the energy loss. Inelastic interactions include phonon excitations,inter- and intra-band transitions,plasmon excitations,inner shell ionizations,and Cherenkov radiation. The inner-shell ionizations are particularly useful for detecting the elemental components of a material. For example,one might find that a larger-than-expected number of electrons comes through the material with 285 eV less energy than they had when they entered the material. This is approximately the amount of energy needed to remove an inner-shell electron from a carbon atom,which can be taken as evidence that there is a significant amount of carbon present in the sample. With some care,and looking at a wide range of energy losses,one can determine the types of atoms,and the numbers of atoms of each type,being struck by the beam. The scattering angle can also be measured,giving information about the dispersion relation of whatever material excitation caused the inelastic scattering.
In electromagnetism,Brillouin scattering,named after Léon Brillouin,refers to the interaction of light with the material waves in a medium. It is mediated by the refractive index dependence on the material properties of the medium;as described in optics,the index of refraction of a transparent material changes under deformation.
In physics,Raman scattering or the Raman effect is the inelastic scattering of photons by matter,meaning that there is both an exchange of energy and a change in the light's direction. Typically this effect involves vibrational energy being gained by a molecule as incident photons from a visible laser are shifted to lower energy. This is called normal Stokes-Raman scattering.
Jan Peter Toennies is a German-American scientist.
In condensed matter physics,second sound is a quantum mechanical phenomenon in which heat transfer occurs by wave-like motion,rather than by the more usual mechanism of diffusion. Its presence leads to a very high thermal conductivity. It is known as "second sound" because the wave motion of entropy and temperature is similar to the propagation of pressure waves in air (sound). The phenomenon of second sound was first described by Lev Landau in 1941.
Helium atom scattering (HAS) is a surface analysis technique used in materials science. It provides information about the surface structure and lattice dynamics of a material by measuring the diffracted atoms from a monochromatic helium beam incident on the sample.
In solid state physics,a surface phonon is the quantum of a lattice vibration mode associated with a solid surface. Similar to the ordinary lattice vibrations in a bulk solid,the nature of surface vibrations depends on details of periodicity and symmetry of a crystal structure. Surface vibrations are however distinct from the bulk vibrations,as they arise from the abrupt termination of a crystal structure at the surface of a solid. Knowledge of surface phonon dispersion gives important information related to the amount of surface relaxation,the existence and distance between an adsorbate and the surface,and information regarding presence,quantity,and type of defects existing on the surface.
Giacinto Scoles is a European and North American chemist and physicist who is best known for his pioneering development of molecular beam methods for the study of weak van der Waals forces between atoms,molecules,and surfaces. He developed the cryogenic bolometer as a universal detector of atomic and molecule beams that not only can detect a small flux of molecules,but also responds to the internal energy of the molecules. This is the basis for the optothermal spectroscopy technique which Scoles and others have used to obtain very high signal-to noise and high resolution ro-vibrational spectra.
Interfacial thermal resistance,also known as thermal boundary resistance,or Kapitza resistance,is a measure of resistance to thermal flow at the interface between two materials. While these terms may be used interchangeably,Kapitza resistance technically refers to an atomically perfect,flat interface whereas thermal boundary resistance is a more broad term. This thermal resistance differs from contact resistance because it exists even at atomically perfect interfaces. Owing to differences in electronic and vibrational properties in different materials,when an energy carrier attempts to traverse the interface,it will scatter at the interface. The probability of transmission after scattering will depend on the available energy states on side 1 and side 2 of the interface.
Adrian Frederick George Wyatt,FRS is a British physicist,and Emeritus Professor at University of Exeter. He is a member of the Quantum Systems and Nanomaterials group. He won the 2004 Fernand Holweck Medal and Prize of the Institute of Physics.
Nuclear resonance vibrational spectroscopy is a synchrotron-based technique that probes vibrational energy levels. The technique,often called NRVS,is specific for samples that contain nuclei that respond to Mössbauer spectroscopy,most commonly iron. The method exploits the high resolution offered by synchrotron light sources,which enables the resolution of vibrational fine structure,especially those vibrations that are coupled to the position of the Fe centre(s). The method is popularly applied to problems in bioinorganic chemistry,materials science,and geophysics. A novel aspect of the method is the ability to determine the 3D-trajectory of iron atoms within vibrational modes,providing a unique appraisal of DFT-prediction accuracy. Other names for this method include nuclear inelastic scattering (NIS),nuclear inelastic absorption (NIA),nuclear resonant inelastic x-ray scattering (NRIXS),and phonon assisted Mössbauer effect.
The EPS CMD Europhysics Prize is awarded since 1975 by the Condensed Matter Division of the European Physical Society,in recognition of recent work by one or more individuals,for scientific excellence in the area of condensed matter physics. It is one of Europe’s most prestigious prizes in the field of condensed matter physics. Several laureates of the EPS CMD Europhysics Prize also received a Nobel Prize in Physics or Chemistry.
Brillouin spectroscopy is an empirical spectroscopy technique which allows the determination of elastic moduli of materials. The technique uses inelastic scattering of light when it encounters acoustic phonons in a crystal,a process known as Brillouin scattering,to determine phonon energies and therefore interatomic potentials of a material. The scattering occurs when an electromagnetic wave interacts with a density wave,photon-phonon scattering.
The helium dimer is a van der Waals molecule with formula He2 consisting of two helium atoms. This chemical is the largest diatomic molecule—a molecule consisting of two atoms bonded together. The bond that holds this dimer together is so weak that it will break if the molecule rotates,or vibrates too much. It can only exist at very low cryogenic temperatures.
Elias Burstein was an American experimental condensed matter physicist whose active career in science spanned seven decades. He is known for his pioneering fundamental research in the optical physics of solids;for writing and editing hundreds of articles and other publications;for bringing together scientists from around the world in international meetings,conferences,and symposia;and for training and mentoring dozens of younger physicists.
Helium-3 surface spin echo (HeSE) is an inelastic scattering technique in surface science that has been used to measure microscopic dynamics at well-defined surfaces in ultra-high vacuum. The information available from HeSE complements and extends that available from other inelastic scattering techniques such as neutron spin echo and traditional helium-4 atom scattering (HAS).
Brent Fultz is an American physicist and materials scientist and one of the world's leading authorities on statistical mechanics,diffraction,and phase transitions in materials. Fultz is the Barbara and Stanley Rawn Jr. Professor of Applied Physics and Materials Science at the California Institute of Technology. He is known for his research in materials physics and materials chemistry,and for establishing the importance of phonon entropy to the phase stability of materials. Additionally,Fultz oversaw the construction of the wide angular-range chopper spectrometer (ARCS) instrument at the Spallation Neutron Source and has made advances in phonon measuring techniques.
Bretislav Friedrich is a Research Group leader at the Department of Molecular Physics,Fritz-Haber-Institut der Max-Planck-Gesellschaft and Honorarprofessor at the Technische Universität in Berlin,Germany. He is globally recognized for his pioneering research surrounding interaction of molecules with and in electric,magnetic,and optical fields as well as on cold molecules. He was admitted to the Learned Society of the Czech Republic in 2011.
Kwong-Tin Tang is an engineer,academic and researcher. He is an Emeritus Professor of Physics at the Pacific Lutheran University,Tacoma.
