Desorption and trapping of argon at a 2H--W(100) surface and a test of the applicability of detailed balance to a nonequilibrium system

Journal Article · Sat Apr 01 00:00:00 EST 1989 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.455838· OSTI ID:6392691

Rettner, C T; Schweizer, E K; Mullins, C B

Molecular beam techniques have been used to probe the dynamics of the trapping and trapping--desorption of Ar at a hydrogen-saturated W(100) surface. Trapping probabilities have been measured as a function of incidence energy E/sub i/, and angle theta/sub i/ for a surface temperature T/sub s/ of 85 K. We find that this probability scales approximately with E/sub i/ cos theta/sub i/, rather than E/sub i/ or the so-called ''normal energy'' E/sub i/ cos/sup 2/ theta/sub i/. Trapping probabilities approach unity for low energies, falling to 0.5 and 0.05 for E/sub i/ cos theta/sub i/ approx.30 and 100 meV, respectively. The time-of-flight distributions of scattered Ar are clearly bimodal in many cases, having both direct--inelastic and trapping--desorption components. The latter component has been characterized over a wide range of conditions to provide information on the desorption of Ar from this surface. We find that desorbing species emerge with a near-cosine angular distribution for T/sub s/ approx. =85 K. However, these distributions become increasingly noncosine as T/sub s/ is raised, becoming substantially broader than cosine. In addition, at the lowest temperature employed (approx.85 K), the velocity distributions of the desorbing atoms are well described by Maxwell--Boltzmann distributions characteristic of the surface temperature. At higher temperatures, these distributions are still approximately Boltzmann, but the characteristic temperature falls below T/sub s/.

• Research Organization: IBM Almaden Research Center, K33/801, San Jose, California 95120-6099
• OSTI ID: 6392691
• Journal Information: J. Chem. Phys.; (United States), Vol. 90:7
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ARGON
DESORPTION
TRAPPING
TUNGSTEN
SORPTIVE PROPERTIES
HYDROGEN
INCIDENCE ANGLE
MOLECULAR BEAMS
BEAMS
ELEMENTS
FLUIDS
GASES
METALS
NONMETALS
RARE GASES
SURFACE PROPERTIES
TRANSITION ELEMENTS
656003* - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)