Electron and Photon Stimulated Desorption (BES 2)
Quick Specs
- Sample temperature range of 50 K to 1200 K
- Low-energy pulsed electron gun energy range of 5 eV to 100 eV
- Beam spot size of 1.5 mm
EMSL's non-thermal interfacial reactions instrumentation is available for use in research directed toward understanding non-thermal interfacial processes. Much radiation damage occurs due to the many secondary electrons produced when high-energy radiation penetrates a material. Using this instrumentation, researchers can probe the details of radiation "damage" on both clean and adsorbate-covered surfaces by observing the effects of low-energy electron bombardment of samples. Studies of amorphous ice, as well as a newly developed liquid beam source, permit investigation of non-thermal processes in both liquids and at liquid interfaces. For example, researchers have conducted low-energy (5 eV to 150 eV) electron- and ultraviolet (6 eV to 12 eV) photon-stimuated desorption, dissociation, and inelastic reactive scattering studies in thin films of ice. Similar studies are being performed on metal oxide and salt substrates.
All work with these instruments must be performed in compliance with EMSL practices and permits.
Electron Stimulated Desorption (BES 1)
A small ultrahigh vacuum chamber is available for studies of electron-stimulated desorption. The chamber has a base pressure of 1 × 10-10 Torr and is equipped with a low-energy (5 eV to 100 eV) pulsed electron gun; a quadrupole mass spectrometer; an effusive gas doser; and a time-of-flight (TOF) mass spectrometer. The pulsed electron beam has an energy spread of ~0.3 eV, a typical current density of 1014 electrons/cm2/s (continuous beam), and a beam spot size of ~1.5 mm. The sample is mounted on a rotatable flange and is in thermal contact with a liquid nitrogen reservoir. Quartz windows on the chamber allow access for laser detection of desorbed species.
Electron and Photon Stimulated Desorption (BES 2)
A much larger ultrahigh vacuum chamber has been designed for both photon- and electron-stimulated desorption studies. This chamber contains a cryocooled sample holder on a double rotary flange. The sample can be cooled as low as 50 K or heated to 1200 K for cleaning. The sample holder contains provisions for mounting two samples plus a Faraday cup, any one of which can be rotated into the line of a pulsed low-energy electron beam similar to the one found in BES 1. Alternatively, the samples can be illuminated by externally generated laser beams (tunable 200 nm to 700 nm or fixed at 193 nm or 157 nm). Both TOF and quadrupole mass spectrometry are available for analyzing desorption products. The TOF system is specifically designed for the detection of neutral products using sensitive quantum-state resolved laser ionization techniques. In addition, samples can be cleaned with a sputter gun and characterized by Auger electron spectroscopy. A typical base pressure of 1 × 10-10 Torr is reached by a combination of an ultrahigh vacuum turbo pump and cryocooled titanium sublimation pump.
All Related Publications Related Publications
- Nonthermal Water Splitting on Rutile TiO2: Electron-Stimulated Production of H-2 and O-2 in Amorphous Solid Water Films on TiO2(110).
- Imaging Consecutive Steps of O2 Reaction with Hydroxylated TiO₂(110): Identification of HO₂ and Terminal OH Intermediates.
- Electron-Stimulated Reactions and O-2 Production in Methanol-Covered Amorphous Solid Water Films.
- Water as a Catalyst: Imaging Reactions of O-2 with Partially and Fully Hydroxylated TiO2(110) Surfaces.
- Two Pathways for Water Interaction with Oxygen Adatoms on TiO2(110).
