Evidence for coupled rotational and phonon quantum excitation in the scattering of a nearly monoenergetic HD beam from the Ni(001) surface

Journal Article · Mon Jan 15 04:00:00 EST 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.458105· OSTI ID:7021660

Berndt, R; Toennies, J P; Woell, C ^[1]

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1. Max-Planck-Institut f uer Stroemungsforschung, Bunsenstrasse 10, 3400 Goettingen, Federal Republic of Germany (DE)

Angular distributions and time-of-flight spectra of a nearly monoenergetic ({Delta}{ital v}/{ital v}{congruent}2% FWHM) He seeded HD beam ({ital k}{sub {ital i}}=6.80 A{sup {minus}1}, {ital E}{sub {ital i}}=32 meV) have been measured after scattering from a Ni(001) single-crystal surface along the {l angle}100{r angle} azimuth. The most intense peaks in the angular distributions are attributed to diffraction with rotational excitation while the rotationally elastic diffraction peaks are an order of magnitude smaller. All the time-of-flight distributions reveal intense peaks at {Delta}{ital E}={minus}11.06 meV corresponding to the HD rotational transition {ital j}{sub {ital i}}=0{r arrow}{ital j}{sub {ital f}}=1. The rotational energy loss observed at angles between the diffraction peaks is attributed to incoherent inelastic scattering at defects. The other inelastic peaks in the time-of-flight spectra can be assigned to phonons which are created or annihilated in the rotationally inelastic collisions. The measured phonon dispersion curves suggest a predominant interaction with the transverse bulk edge and not with the Rayleigh mode. These results provide the first direct evidence for a coupling of rotational transitions to the phonons of a metal surface. The pronounced rotational inelasticity at step edges does not support the widely held view that nonactivated chemisorption occurs at step edges.

• OSTI ID: 7021660
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 92:2; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANGULAR DISTRIBUTION
BEAMS
COLLISIONS
DEUTERIDES
DEUTERIUM COMPOUNDS
DISTRIBUTION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
HYDROGEN COMPOUNDS
HYDROGEN DEUTERIDE
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
NICKEL
PHONONS
QUASI PARTICLES
ROTATIONAL STATES
SURFACES
TIME-OF-FLIGHT METHOD
TRANSITION ELEMENTS