The monolayer : an FTIRS, LEED and HAS study

Weiß, Helmut

doi:10.1016/0039-6028(95)00072-0

Cited by 12 publications

(7 citation statements)

References 27 publications

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“…Similar red shifts of the ν 1 band have also been observed on NaCl(001), R-Cr 2 O 3 powder, as well as in molecular complexes, where the N 2 O is bound to cationic transition metals, such as Ru. [40][41][42][43] In the case of R-Cr 2 O 3 powder, the red shifted bands in the ν 1 stretch region were assigned to N 2 O molecules bound with the oxygen end down. 42,43…”

Section: Resultsmentioning

confidence: 99%

N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

et al. 2010

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The adsorption of N2O on the surface of MgO(001) thin films has been studied at low temperature (60 K) using infrared reflection−absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD). The observed infrared spectrum consists of several components indicating different adsorption sites for N2O. The different IR peaks can be related to particular thermal desorption features by combining the TPD spectra with temperature-dependent infrared measurement. By comparing spectra from films with different roughness and different supports, a band at 2236 cm−1 can be assigned to N2O adsorbed on the MgO terraces, while peaks at the higher frequency are assigned to molecules adsorbed on low-coordinated sites.

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Section: Resultsmentioning

confidence: 99%

N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

et al. 2010

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“…In order to study the translational symmetry of the adsorbate, it can be attempted to employ low energy electron diffraction (LEED), though electron-induced reaction may take place. Using SPA-LEED (spot profile analysis) [62] at extremely low electron current and short measuring time sufficiently high sensitivity is achieved without affecting detectibly the adsorbate [63]. Theoretical studies support the experiments.…”

Section: Introductionmentioning

confidence: 73%

“…Polarization Fourier transform infrared surface spectroscopy (PIRS), in combination with a diffraction technique, LEED or HAS (helium atom scattering) has been applied to observe the localized, as well as the collective, vibrations of simple molecules physisorbed on ionic single crystal surfaces: H 2 , CO, CO 2 , H 2 O, N 2 O, COS on NaCl(100) [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]; CO, CO 2 and N 2 O, H 2 O on MgO(001) [54][55][56][57][58][59], respectively, and others. PIRS has the advantage of being non-invasive, which is necessary for the study of adsorbed reactive, thermolabile and photosensitive HN 3 .…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Hydrogen Azide on the NaCl(100) Single Crystal Surface. Orientational and Translational Ordering of the HN3 Monolayer as Revealed by PIRS, LEED and Spectra Simulation

Heidberg¹,

Hustedt²,

Oppermann³

et al. 2001

Zeitschrift Für Physikalische Chemie

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The adsorption of hydrogen azide HN 3 on NaCl(100) has been studied by means of polarization Fourier transform infrared spectroscopy PIRS and low energy electron diffraction LEED. The well-defined surface was prepared in-situ under UHV by cleaving a single crystal with as few dislocations as possible.Ordered molecular adsorption of HN 3 has been observed. Multiple absorptions of all four molecular vibrations with frequencies between 4000 and 1000 cm −1 , all nondegenerate in the gas, are found at 120 K. In particular, a quartet of strongly polarized sharp absorption lines for the asymmetric stretching vibration ν 2 at 2162.8, 2154.0, 2149.2, and 2138.3 cm −1 is obtained, the line at 2162.8 cm −1 being extremely weak in s-polarization. Saturation of adsorption, indicating the monolayer, is observed both upon dosing HN 3 in the low coverage range, where island growth is inferred, and desorbing HN 3 from multilayers. No domain orientation appears to be preferred. An activation energy of desorption of 43 ± 5 kJ/mol and a pre-exponential factor of 2.6 × 10 14±1.5 s −1 were determined.Isotopic mixture experiments with H 14 N 3 and H 14 N 15 N 14 N reveal that the four absorption lines of the ν 2 vibration are caused first by site splitting due to two energetically inequivalent HN 3 -species and second by Davydov splitting due to a strong correlation field between the dynamic dipoles. There are four molecules per adsorbate unit cell: two different pairs of energetically equivalent but translationally inequivalent molecules. Further, two different pairs of NH hydrogen bonds are observed. Tilt angles and intermolecular angles of the adsorbed molecules were determined. The translational symmetry of the adsorbate was derived by LEED. Simulation of the ν 2 quartet spectrum based on equations of classical electrodynamics was accomplished yielding the angles, lateral distances and dynamic vibrational couplings within the monolayer. Combining all results we propose a monolayer structure of angularly ordered zigzag chains of HN 3 molecules, where two molecules are linked by a hydrogen bond forming a dimer, while the other weaker hydrogen bond ties the dimers together or to a Cl − surface ion. Two HN 3 dimers make up the p(2 × 2) monolayer unit cell of 2D space group pg.

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“…In order to employ the three independent experimental methods different setups have been used, which are described in detail elsewhere (HAS in [15][16][17][18], SPA-LEED in [18], PIR in [19]). The NaCI(OOI) faces were prepared by cleavage in ultrahigh vacuum (HAS, PIR) or using nitrogen as protective gas (SPA-LEED), respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Diffraction of low-energy electrons from bare NaCI(OOI) and monolayer CH 4-NaCI(001) was studied employing a high-resolution SPA-LEED instrument [22] which has been applied successfully to e.g. N 20-NaCI(001) [18] and CO rMgO(OO1) [23]. Similar to the HAS experiments the coverage was monitored by following the integrated (0,0) spot intensity during the CH 4 inlet.…”

Section: 2 Electron Diffraction (Sp A-leed)mentioning

confidence: 99%

A PIR, HAS and LEED Study of the Monolayer CH₄‐NaCl(001)

Heidberg

Schönekäs

Weiß

et al. 1995

Ber Bunsenges Phys Chem

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The adsorbate CH4‐NaCl(001) at monolayer coverage has been studied by means of helium atom scattering (HAS), electron diffraction (SPA‐LEED) and polarization Fourier‐transform infrared spectroscopy (PIR) in the temperature range between 45 K and 10 K. Above 40 K a splitting of the v4 mode of CH4 into a polarization‐dependent doublet absorption was observed in the FTIR spectra. HAS and SPA‐LEED measurements reveal a (1×1) superstructure with one CH4 molecule per NaCl ion pair. Calculations of the potential energy support these experimental results, yielding a perfect dipod arrangement of the CH4 molecules in the (1×1) structure. Isosteric cooling of the adsorbate results in a two‐dimensional phase transition of order > 1. By means of HAS a p(2×2) superstructure was found at T < 30 K, whereas SPA‐LEED suggests a (2×1) symmetry. Beside of a remarkable sharpening of all IR absorptions two additional features are observed. The phase transition is reversible. Two to three hours after preparation both diffraction methods yield the (1×1) structure even at lowest temperatures. This time behaviour may be indicative of a quantum effect, namely nuclear spin conversion, in the adsorbed methane layer. Knowledge of the interaction between CH4 and NaCl is necessary to predict the gas migration and therewith the safety aspects for a final repository of nuclear waste in permian salt domes.

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The monolayer : an FTIRS, LEED and HAS study

Cited by 12 publications

References 27 publications

N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

Adsorption of Hydrogen Azide on the NaCl(100) Single Crystal Surface. Orientational and Translational Ordering of the HN3 Monolayer as Revealed by PIRS, LEED and Spectra Simulation

A PIR, HAS and LEED Study of the Monolayer CH₄‐NaCl(001)

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The monolayer : an FTIRS, LEED and HAS study

Cited by 12 publications

References 27 publications

N2O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

N2O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

Adsorption of Hydrogen Azide on the NaCl(100) Single Crystal Surface. Orientational and Translational Ordering of the HN3 Monolayer as Revealed by PIRS, LEED and Spectra Simulation

A PIR, HAS and LEED Study of the Monolayer CH4‐NaCl(001)

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N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

N₂O Adsorption on the Surface of MgO(001) Thin Films: An Infrared and TPD Study

A PIR, HAS and LEED Study of the Monolayer CH₄‐NaCl(001)