Chemically Induced Electronic Excitations at Metal Surfaces

• Published in: Science (American Association for the Advancement of Science) Vol. 294; no. 5551; pp. 2521 - 2523
• Main Authors: Gergen, Brian, Nienhaus, Hermann, Weinberg, W. Henry, McFarland, Eric W.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 21.12.2001; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Adsorption; Biological and medical sciences; Charge carriers; Chemical reactions; Chemisorption; Desorption; Diodes, Schottky-barrier; Electric current; Electrochemistry; Electron-electron interactions; Electrons; Energy; Fundamental and applied biological sciences. Psychology; Gases; Hot electrons; Metal surfaces; Metals; Molecular and cellular biology; Observations; Schottky diodes
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1066134

The energy released in low-energy chemisorption or physisorption of molecules on metal surfaces is usually expected to be dissipated by surface vibrations (phonons). Theoretical descriptions of competing electronic excitations are incomplete, and experimental observation of excited charge carriers has been difficult except at energies high enough to eject electrons from the surface. We observed reaction-induced electron excitations during gas interactions with polycrystalline silver for a variety of species with adsorption energies between 0.2 and 3.5 electron volts. The probability of exciting a detectable electron increases with increasing adsorption energy, and the measured time dependence of the electron current can be understood in terms of the strength and mechanism of adsorption.