dc.contributor.advisor | Toennies, Jan Peter Prof. Dr. | de |
dc.contributor.author | Traeger, Franziska | de |
dc.date.accessioned | 2013-01-31T07:54:21Z | de |
dc.date.available | 2013-01-31T07:54:21Z | de |
dc.date.issued | 2001-09-24 | de |
dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-000D-F212-2 | de |
dc.identifier.uri | http://dx.doi.org/10.53846/goediss-3584 | |
dc.format.mimetype | application/pdf | de |
dc.language.iso | ger | de |
dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/3.0/ | de |
dc.title | Streuexperimente mit Wasserstoff- und Heliumstrahlen zur Untersuchung der Wechselwirkung von H2, N2 und C2H2 mit den (001)-Oberflächen von LiF, NaCl, KCl und MgO | de |
dc.type | doctoralThesis | de |
dc.title.translated | Scattering experiments with molecular hydrogen and helium beams investigating the interactions of H2, N2 and C2H2 with the (001) surfaces of LiF, NaCl, KCl and MgO | de |
dc.contributor.referee | Toennies, Jan Peter Prof. Dr. | de |
dc.date.examination | 2001-02-01 | de |
dc.subject.dnb | 29 Physik, Astronomie | de |
dc.subject.gok | RVE200 | de |
dc.description.abstracteng | In the present work the interaction of
hydrogen, nitrogen and acetylene with the surfaces of ionic
crystals has been investigated. These studies use the scattering of
molecular hydrogen beams from clean surfaces as well as information
on structure and dynamics of molecular adsorbates obtained from
elastic and inelastic helium atom scattering. In the scattering of
H2 from the (001) surfaces of LiF, NaCl, KCl and MgO differences in
the diffraction intensities between beams of normal-H2 ('n': 75 %
ortho j = 1 und 25 % para j = 0) and para-H2 ('p': j = 0) have been
observed. This effect can be attributed to the dependence of the
electrostatic interaction of the molecular quadrupole moment with
the gradient of the surface field on the orientation of the
molecule. Helium diffraction from n-H2, p-H2, HD and D2 adsorbed on
NaCl is consistent with (1 x 1) superstructures proposed in the
literature. Time-of-flight spectra reveal several well resolved,
dispersionless peaks, which can be assigned to a vibration parallel
to the surface (7 meV for p-H2), anharmonic overtones (12 meV and
17 meV for p-H2) as well as double excitations of the fundamental
vibrational mode. The external vibrational modes of o-H2 and p-H2
differ by about 1 meV, which again can be attributed of the
different electrostatic interaction with the surface. Hydrogen
adsorbed on MgO shows the series of c(2 x 2) - c(4 x 2) - c(6 x 2)
structures as the coverage is increased followed by condensation of
the second layer. Along the [110] direction two dispersionless
modes have been measured for the c(4 x 2) phase at 8.5 and 10.5
meV, as well as a dispersive mode between 2 and 6 meV. The dynamics
of the c(6 x 2) phase is similar. The second layer reveals only one
dispersionless mode at around 5 meV. For comparison, the adsorbate
N2/MgO has also been investigated. Acetylene adsorbed on KCl has
been investigated between monolayer coverage and 40 layers. From
diffraction measurements a (sqrt2 x sqrt2)R45° symmetry has been
determined for the monolayer as well as for thicker layers. For the
multilayers this symmetry corresponds to the orthorhombic
modification of bulk acetylene. With inelastic helium atom
scattering four rather strongly dispersive modes below 14 meV have
been measured, which can be assigned to parallel, perpendicular and
see-saw modes. Thicker layers display a Rayleigh mode with an
energy of 6 meV at the zone boundary and three additional
modes. | de |
dc.contributor.coReferee | Winzer, Klaus Prof. Dr. | de |
dc.subject.eng | molecular adsorbates | de |
dc.subject.eng | structure and dynamics | de |
dc.subject.eng | insulating surfaces | de |
dc.subject.eng | helium atom scattering | de |
dc.subject.eng | hydrogen molecular beam diffraction | de |
dc.subject.bk | 33.68 | de |
dc.identifier.urn | urn:nbn:de:gbv:7-webdoc-1093-9 | de |
dc.identifier.purl | webdoc-1093 | de |
dc.identifier.ppn | 335726569 | |