Rotational dynamics and electronic energy partitioning in the electron‐stimulated desorption of NO from Pt(111)

1988 ◽  
Vol 6 (3) ◽  
pp. 895-898 ◽  
Author(s):  
A. R. Burns ◽  
E. B. Stechel ◽  
D. R. Jennison
Keyword(s):  
Electronic Energy ◽  
Energy Partitioning ◽  
Rotational Dynamics ◽  
Electron Stimulated Desorption

Electronic Energy Partitioning in the Reactions of Metastable Mg*(3PJ) Atoms with F2, Cl2, Br2, I2, ICl, IBr

2000 ◽  
Vol 55 (3-4) ◽  
pp. 433-440
Author(s):  
P. Kierzkowski ◽  
B. Pranszke ◽  
A. Kowalski ◽  
M. Menzinger
Keyword(s):  
Information Theory ◽  
Cross Sections ◽  
Electronic Energy ◽  
Energy Partitioning ◽  
Entrance Channel ◽  
Quantum Yields ◽  
Total Attenuation

Abstract Chemiluminescent reactions of metastable Mg*(3PJ) atoms with F2 , Cl2 , Br2 , I2 , IC1, IBr molecules were studied in a beam-gas experiment. For all homonuclear targets the MgX(A 2Π -X 2Σ+) emission was observed, but for IC1 and IBr reactants the Mgl(A-X) emission was absent and only MgCl(A-X) or MgBr(A-X) spectra were found. In addition, for the I2 , IBr, IC1, Br2 reactions, broad pseudocontinua extend from above 400 nm into the infrared. These pseudocontinua are ten-tatively attributed to the Mgl, MgBr (B' 2Σ+ -X2Σ+) transition. The total attenuation cross sections, chemiluminescence cross sections and quantum yields were measured. The quantum yields are all below 5%. The results are analyzed using information theory. The low yields for the Mg* + F2 system are explained by a barrier in the entrance channel. For other reactions the low yields are most probably caused by predissociation of the MgX*(A 2Π) products

Electron-beam damage of oxides at high current densities

1989 ◽  
Vol 47 ◽  
pp. 634-635
Author(s):  
M. R. McCartney ◽  
J. K. Weiss ◽  
David J. Smith
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Current Density ◽  
Transition Metal Oxides ◽  
Time Resolved ◽  
Rapid Acquisition ◽  
Resolution Electron ◽  
Current Densities ◽  
Electron Stimulated Desorption ◽  
Channel Analyzer

It is well-known that electron-beam irradiation within the electron microscope can induce a variety of surface reactions. In the particular case of maximally-valent transition-metal oxides (TMO), which are susceptible to electron-stimulated desorption (ESD) of oxygen, it is apparent that the final reduced product depends, amongst other things, upon the ionicity of the original oxide, the energy and current density of the incident electrons, and the residual microscope vacuum. For example, when TMO are irradiated in a high-resolution electron microscope (HREM) at current densities of 5-50 A/cm2, epitaxial layers of the monoxide phase are found. In contrast, when these oxides are exposed to the extreme current density probe of an EM equipped with a field emission gun (FEG), the irradiated area has been reported to develop either holes or regions almost completely depleted of oxygen. ’ In this paper, we describe the responses of three TMO (WO3, V2O5 and TiO2) when irradiated by the focussed probe of a Philips 400ST FEG TEM, also equipped with a Gatan 666 Parallel Electron Energy Loss Spectrometer (P-EELS). The multi-channel analyzer of the spectrometer was modified to take advantage of the extremely rapid acquisition capabilities of the P-EELS to obtain time-resolved spectra of the oxides during the irradiation period. After irradiation, the specimens were immediately removed to a JEM-4000EX HREM for imaging of the damaged regions.

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