Low-energy vibrational modes of the monolayer adsorbate CO2/NaCl(001)

Lange, Gerrit; Toennies, J. P.; Vollmer, R.; Weiß, Helmut

doi:10.1063/1.464399

Cited by 33 publications

(11 citation statements)

References 30 publications

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“…Similar dispersionless adsorbate phonon modes have been observed previously for a number of other monolayer systems. 6,25 In spite of the lack of sufficient signal to determine any dispersion of the E 2 mode, it is also tentatively assigned to some form of frustrated adsorbate vibrational motions. Additional information on the identities of these modes is provided by TOF measurements on the corresponding C 2 D 2 adlayer.…”

Section: Inelastic Helium Atom Scattering Resultsmentioning

confidence: 99%

Phonon-libron dynamics of acetylene adsorbed onNaCl(001)

et al. 1998

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The phonon-dispersion curves of the high-temperature (3ͱ2ϫͱ2)R45°phase of acetylene on NaCl͑001͒ have been measured using high-resolution time-of-flight inelastic helium-atom scattering and compared with semiempirical calculations. The observed two Einstein vibrational modes at 8 and 14 meV are assigned to a collective perpendicular motion of the molecule centers of mass in the monolayer and to a collective librational motion of the molecular axes, respectively. With the same semiempirical potential used in the dynamical calculations, the 0 K adsorbate monolayer structure is predicted to be (ͱ2ϫͱ2)R45°which is at variance with the (7ͱ2ϫͱ2)R45°structure determined at TϽ80 K by helium diffraction. The results are compared with structure assignments based on infrared spectroscopy and ab initio calculations.

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Section: Inelastic Helium Atom Scattering Resultsmentioning

confidence: 99%

Phonon-libron dynamics of acetylene adsorbed onNaCl(001)

et al. 1998

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“…Both the several distinct environments for the molecules in that structure and its higher density lead to the expectation that there would be considerable dispersion as seen, for example, with CO 2 on NaCl. 18 Finally, various models of the physisorption potentials were assessed. Large contributions to the energy were found to arise from the interaction of the distributed molecular charge distributions with the very nonuniform electrostatic fields at the surface of the NaCl crystal.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the HAS angular distributions from the NaCl films exhibit significantly lower diffraction peak intensities as well as higher background intensity levels for any mode of film preparation ͑different crystal temperatures during the film deposition, different annealing time, and temperatures, etc.͒. Although, earlier experiments with other adsorbates showed good agreement between the HAS and the LEED data 18,57 we conjecture that the situation may differ for water, since water adsorption on surfaces is anticipated to depend strongly on the defect structure of the substrate. For example, in related experiments on water adsorption on the Cu͑111͒ surface Hinch and Dubois 58 demonstrated that two phases of water ͑metastable and stable͒ can be formed depending on the defect concentration consisting of steps or contaminants.…”

Section: ͑3͒mentioning

confidence: 92%

“…Helium scattering has previously been used to study a number of adsorbates on similar insulating substrates. [17][18][19] Sharp rises have been found in the adsorption isotherms of H 2 O/NaCl͑100͒ at room temperature 20 and at 140 K, 11,12 which indicate that there is condensation of at least a monolayer of water on NaCl͑100͒ before 3D phases form. The heats of adsorption are in the range 50-60 kJ mol Ϫ1 , 12,13 and the corresponding heats of vaporization and sublimation of bulk water/ice are 45 and 51 kJ mol Ϫ1 , respectively.…”

Section: Introductionmentioning

confidence: 98%

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A helium atom scattering study of water adsorption on the NaCl(100) single crystal surface

Bruch¹,

Glebov²,

Toennies³

et al. 1995

The Journal of Chemical Physics

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A helium atom scattering study of the structure and dynamics of a Xe monolayer on NaCl(001) Structural and dynamic properties of H 2 O adsorbed on an in situ cleaved NaCl͑100͒ crystal surface were studied by He atom scattering in the range of temperatures and partial pressures of 80-160 K and 5ϫ10 Ϫ7 -5ϫ10 Ϫ10 mbar, respectively. A well-ordered 2D H 2 O layer was formed during adsorption as well as by heating of 3D ice. The isosteric heat of adsorption in the monolayer regime was found to be in the range 58 -63 kJ/mol. The structure of the 2D condensed phase was investigated for both modes of preparation and in both cases a ͑1ϫ1͒ diffraction pattern was found. Time-of-flight spectra of the monolayer H 2 O/NaCl were measured in the ͗100͘ direction and phonon dispersion curves were determined. The observed dispersion-free vibrational mode, with បϭ5.5 meV, was identified as a frustrated translation of the water molecule parallel to the surface, via calculations for physisorption models of the H 2 O/NaCl interaction. Other salient features of the adsorption, the large heat of adsorption, and the magnitude of the frequency of molecular vibration perpendicular to the substrate, are reproduced in the calculations.

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“…19) qv so that we again arrive at (A 1.13). Thus, the infinitesimal imaginary addition at the pole of the GF (A1.15) really arises from the theta-function in Eq.…”

Section: Gg(o))= \Co -O)g V Jmentioning

confidence: 94%

Back Matter

2002

World Scientific Lecture and Course Notes in Chemistry

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The Hamiltonian function for a system of bound harmonic oscillators is, in the most general form, a sum of two positively definite quadratic forms composed of the particle momentum vectors and the Cartesian projections of particle displacements about equilibrium positions:where m, is the mass of the ith particle; $ denotes the force constants; a, /} are the projections of corresponding vectors on the Cartesian coordinate axes (summation over Greek indices will be indicated explicitly because it appears in the expressions more than twice). The equations of motion for the displacements u" that correspond

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Low-energy vibrational modes of the monolayer adsorbate CO2/NaCl(001)

Cited by 33 publications

References 30 publications

Phonon-libron dynamics of acetylene adsorbed onNaCl(001)

Phonon-libron dynamics of acetylene adsorbed onNaCl(001)

A helium atom scattering study of water adsorption on the NaCl(100) single crystal surface

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