Molecular desorption induced by energetic ion beam bombardment

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:258333

Chatterjee, R; Riederer, D E; Rosencrance, S W ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States); and others

The bombardment of surfaces by keV ion beams leading to the ejection of clusters and molecular species has found useful application in secondary ion mass spectrometry (SIMS) particularly in the study of organic and biological surfaces. Laser postionization makes it possible to study sputtered neutrals which have a much higher sputter yield. Processes that lead to the transfer of energy of the primary ion beam to the various transitional and internal modes of the desorbed molecule are not very well understood. Of special interest is the question, how the primary ion with an energy of 1-10 keV makes it possible to eject molecular fragments with individual chemical bond strength on the order of 2-10 eV. Mechanisms involving both the motion of atomic nuclei and/or electrons can be responsible for desorption. Energy and angular distributions of sputtered particles give an insight into the ejection mechanisms and the initial configuration of the surface. Initial studies have been done to measure these distributions for various molecular species and atomic clusters. The experimental setup involves the use of laser postionization of the sputtered neutrals in tandem with time-of-flight analysis and a position sensitive detector. The peak in the kinetic energy distributions for the molecules is found to be much lower than those of metal atoms or metal clusters sputtered from clean single crystal metal surfaces. Molecular dynamics calculations have been performed to investigate the nuclear motions in the solid that lead to molecular desorption.

• OSTI ID: 258333
• Report Number(s): CONF-9506225--
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CHEMICAL REACTION YIELD
DESORPTION
DYNAMICS
ION-MOLECULE COLLISIONS
MASS SPECTROSCOPY
MATHEMATICAL MODELS
MOLECULES
TIME-OF-FLIGHT MASS SPECTROMETERS