Site symmetry and correlation field splitting in the adsorbate CO2NaCl(100)

Heidberg, J.; Kampshoff, E.; Kühnemuth, Ralf; Schönekäs, O.; Stein, H.; Weiß, Helmut

doi:10.1016/0039-6028(90)90141-t

Cited by 48 publications

(15 citation statements)

References 8 publications

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“…This adsorption system has become the object of many investigations in recent years (9)(10)(11)(12)(13)(14)(15)(16)(17). In our group a two-dimensional phase transition at pressure p,(T) within the adsorbate has been observed on NaCl(100) samples prepared in air (1 1).…”

Section: Introductionmentioning

confidence: 84%

Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Heidberg¹,

Kampshoff²,

Kühnemuth³

et al. 1994

Can. J. Chem.

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This paper is dedicnted to Professor John C. Polunyi on the occasion of his 65th birthday J. HEIDBERG, E. KAMPSHOFF, R. KUHNEMUTH, and 0. SCHONEKAS. Can. J. Chem. 72, 795 (1994).Two-dimensional sublimation of C 0 2 on NaC1(100), prepared by cleaving a single crystal in situ under ultrahigh vacuum, was observed by polarization Fourier transform infrared spectroscopy. At the transition pressure pl(T) < 1 x lo-'' mbar in the temperature range 45 < T/K < 75 the 2D solid and the ideal 2D lattice gas coexist in a 2D thermodynamic equilibrium.The temperature dependence of the spreading pressure z(T) of the coexisting 2D lattice gas yields the enthalpy of the 2D sublimation AH: D = (3.0 i 0.1) kJImol. In the two-dimensional sublimation reorientation of the C 0 2 molecules takes place; both the polar and the azimuthal molecular angles change.J. HEIDBERG, E. KAMPSHOFF, R. KUHNEMUTH et 0 . SCHONEKAS. Can. J. Chem. 72, 795 (1994). On a observC, par spectroscopie infrarouge i transformation de fourier polarisee, la sublim?tion bi-dimensionnelle du C 0 2 sur du NaCl(100) prCparC par clivage in situ d'un cristal unique sous vide tri's poussi. A la pression de transition p,(T) < 1 x lo-'' mbar dans l'intervalle de tempirature allant de 45 < T/K < 75 le solide 2D et le rCseau 2D gazeux idCal coexistent dans un Cquilibre thermodynamique 2D. L'effet de la tempirature sur 1'Ctalement de la pression z(T) des rCseaux 2D gazeux coexistants donne l'enthalpie de la sublimation 2D AH: D = (3,O i 0,l) kJImol. I1 se produit une rkorientation des molCcules de C 0 2 dans la sublimation bi-dimensionnelle; les deux angles polaire et azimutale changent.[Traduit par la redaction] Introduction In physisorption, the weak interaction between molecules and solids has been studied for many years. A new topic is the stereodynamics of chemical reactions between surface-aligned and oriented physisorbed molecules (1). This paper reports on the thermodynamics of a two-dimensional phase transition with molecular reorientation as revealed by polarization infrared spectroscopy. The system studied is C 0 2 physisorbed on NaC1(100), which can be considered a model for physisorption. It has become important also in geology, in sea spray chemistry, as well as in industrial applications and waste technology. Rock salt in the extended North German salt domes contains, besides the brine inclusions and water from the associated hydrated minerals, primary gases adsorbed on the crystal boundaries or trapped in inclusions. Knowledge of the behaviour of such primary gases as C02, CH4, H20, and HCl is essential when planning the safety aspects for a final repository of radioactive waste in the salt domes (2). To model the behaviour of these simple gases in the salt domes, studies of the gas adsorption on NaCl(100) under well-defined conditions are necessary. Especially those thermodynamic measurements yielding adsorption isotherms, heats of adsorption, and twodimensional phase transitions give insight into the gas-surface interaction. The results can also be used to desc...

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Section: Introductionmentioning

confidence: 84%

Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Heidberg¹,

Kampshoff²,

Kühnemuth³

et al. 1994

Can. J. Chem.

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“…This is a striking example for the influence of surface heterogeneities on the sharpness of 2D transitions, i.e. on the shape of the adsorption isotherms as pointed out for Xe on disordered NaCl(610) and flat NaC1(100), respectively [19].…”

Section: Introductionmentioning

confidence: 97%

“…Physisorption on alkali halide-films, -powders, and -single crystal cleavage planes has been studied by using e. g. volumetric techniques [l -3,6 -101, infrared spectroscopy (IR) [11 -18, 211, Auger electron spectroscopy (AES) [4,19], and X-ray photoelectron spectroscopy [20] yielding adsorption isotherms and isosteric heats of adsorption. In particular, volumetric techniques have been applied to powdered samples: Ar, 02, N2 and C 0 2 on NaCl [6], C2Hs on NaCl and KCl [7], Xe, CH4 and C2H6 on NaCl [S], Kr on NaCl, KCl and RbCl [9], water and alcoholes [lo] as well as Ar, CHI, 02, and N2 on NaF [2].…”

Section: Introductionmentioning

confidence: 99%

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Correlation Field, Two‐Dimensional First Order Phase Transition and Heats of Adsorption in CO₂on the NaCl(100) Cleavage Plane

Heidberg

Kampshoff

Schönekäs

et al. 1990

Ber Bunsenges Phys Chem

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Adsorption 1 Molecular Structure / Phase Transitions 1 Spectroscopy, Infrared Infrared spectra of 13C1602 adsorbed on the NaCl(100) cleavage plane from zero to monolayer coverage 0 and the corresponding adsorption isotherms have been measured. At 0.3 Q , 6 Q 6 Q, , 0, being the C 0 2 monolayer coverage, the vj vibrational band of adsorbed COz shows a doublet structure due to a correlation field, whereas at Q 5 0.3 0, a single band is observed. -The coverage and polarization dependence of the spectra as well as the shape of the isotherms between 80 and 95 K adsorbate temperature reveal a two-dimensional (2D) first order phase transition from a 2D low density phase into a 2D island-like solid. The isosteric heats of adsorption have been determined to be 28.5 kJ rno1-l and 24 kJ mol-' (-10% and +25% error) for Q = 0.08 Qm and Q = 0.96 Q , , respectively. -In the 2D

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“…35 The adsorption energy of a monolayer of CO 2 on NaCl(001) is approximately 0.25 eV. 36 At low coverage the CO 2 molecule is thought to adsorb parallel to the surface midway between adjacent cations with the oxygen atoms directed toward the cations. Theoretical models have been developed for the system.…”

Section: Introductionmentioning

confidence: 99%

Photoinitiated Reaction Dynamics between Aligned Adsorbates on Solid Surfaces: A Theoretical Exploration of the H + CO₂System on LiF(001)

1997

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We report a quasi-classical trajectory study of a chemical reaction between H and CO 2 at the LiF(001) surface. The reaction is initiated by photodissociation of well-aligned HBr(ad) at 193 nm, which produces a "hot" H atom directed toward a nearby CO 2 (ad). Single molecules of each reactant are placed on a static surface, and a full-dimensional HCO 2 potential derived from ab initio calculations is used. The adsorbate-substrate and the adsorbate-adsorbate potentials consist of both nonelectrostatic and electrostatic contributions. Several energetically favorable adsorption configurations are determined by a Monte Carlo method. Quasi-classical trajectories are calculated at 80 K for four different adsorption configurations. We find that the reactivity at some configurations is significantly enhanced compared with the corresponding gas-phase simulation. The calculated impact parameters and incident angles of the surface-aligned collisions indicate that the enhanced reactivity can be largely attributed to the closeness and alignment of the coadsorbates on the surface. Owing to the long-lived complex, product distributions, with the exception of a departure angle, show little memory with regard to the initial configuration and are similar to those obtained in the gas phase. A significant number of the unreacted hydrogen atoms retain sufficient energy to make subsequent reaction with other coadsorbates a possibility. We find evidence of several dynamic features pertinent to the use of the surface as a template for reactivity enhancement, including scattering at the surface, the squeezed atom effect, chattering, and caging.

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Site symmetry and correlation field splitting in the adsorbate CO2NaCl(100)

Cited by 48 publications

References 8 publications

Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Correlation Field, Two‐Dimensional First Order Phase Transition and Heats of Adsorption in CO₂on the NaCl(100) Cleavage Plane

Photoinitiated Reaction Dynamics between Aligned Adsorbates on Solid Surfaces: A Theoretical Exploration of the H + CO₂System on LiF(001)

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Site symmetry and correlation field splitting in the adsorbate CO2NaCl(100)

Cited by 48 publications

References 8 publications

Two-dimensional sublimation of CO2 on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Two-dimensional sublimation of CO2 on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Correlation Field, Two‐Dimensional First Order Phase Transition and Heats of Adsorption in CO2on the NaCl(100) Cleavage Plane

Photoinitiated Reaction Dynamics between Aligned Adsorbates on Solid Surfaces: A Theoretical Exploration of the H + CO2System on LiF(001)

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Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Two-dimensional sublimation of CO₂ on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy

Correlation Field, Two‐Dimensional First Order Phase Transition and Heats of Adsorption in CO₂on the NaCl(100) Cleavage Plane

Photoinitiated Reaction Dynamics between Aligned Adsorbates on Solid Surfaces: A Theoretical Exploration of the H + CO₂System on LiF(001)