Beam-loss spectroscopy

Ramirez-Serrano J, DeGraffenreid W, Weiner J. Beam-loss spectroscopy of cold atoms in a bright sodium beam. Manuscript in preparation to be submitted to Phys. Rev. A. 

In recent years there is a growing interest in the study of vibrational properties of both clean and adsorbate covered surfaces of metals. For several years two complementary experimental methods have been used to measure the dispersion relations of surface phonons on different crystal faces. These are the scattering of thermal helium beams" and the high-resolution electron-energy-loss-spectroscopy. ... 

It would be of great interest to experimentally verify these new results of phonon modes, MSB s and relaxations by suitable methods, such as electron-energy-loss-spectroscopy or thermal helium beam scattering. 

Electron energy loss spectroscopy An analytical technique used to characterize the chemistry, bonding, and electronic structure of thin samples of materials. It is normally performed in a transmission electron microscope. The inelastically scattered electron beams are spectroscopically analyzed to give the energy spectrum of electrons after the interaction. 

The hybridization of carbon atoms is the major structural parameter controlling DLC film properties. Electron energy loss spectroscopy (EELS) has been extensively used to probe this structural feature [5. 6]. In a transmission electron microscope, a monoenergetic electron beam is impinged in a very thin sample, being the transmitted electrons analyzed in energy. Figure 27 shows a typical... 

Figure 5.38. Illustrating the incident electron beam convergence angle (a), the scattering angle (6) and the spectrometer acceptance angle (/l) in electron energy loss spectroscopy. (After Joy, 1981.)...

As noted in the introduction, vibrations in molecules can be excited by interaction with waves and with particles. In electron energy loss spectroscopy (EELS, sometimes HREELS for high resolution EELS) a beam of monochromatic, low energy electrons falls on the surface, where it excites lattice vibrations of the substrate, molecular vibrations of adsorbed species and even electronic transitions. An energy spectrum of the scattered electrons reveals how much energy the electrons have lost to vibrations, according to the formula ... 

The electron-energy-loss spectroscopy (EELS) was performed in transmission with a primary beam energy of 170 keV in a purpose-built UHV spectrometer described in detail elsewhere [5]. For the valence level excitations and elastic scattering (electron diffraction) data the momentum resolution of the instrument was set to 0.04 A 1 with an energy resolution of 90-140 meV. The core level excitations were performed with a momentum and energy resolution of 0.2 A"1 and 90-140 meV, respectively. All EELS experiments were conducted at room temperature. 

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