Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces

Gary N. Robinson, Nicholas Camillone, Paul A. Rowntree, Gang-yu Liu, Jia Wang, Giacinto Scoles

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Low energy helium diffraction has been used to determine the unit mesh parameters of overlayers of CH3Br physisorbed on C(0001), NaCl(001), and LiF(001) at ≈35 K. CH3Br forms a uniaxially commensurate overlayer on C(0001) with unit mesh parameters 4.26 Å × 6.75 Å. On NaCl(001), CH3Br forms a high coverage and a low coverage phase. The high coverage phase is incommensurate and has unit mesh parameters 4.54 Å × 6.73 Å, whereas the low coverage phase is commensurate with a (√2 × 3√2)R 45° unit mesh. The structure of CH3Br/LiF(001) is essentially the same as that of the high coverage phase of CH3Br/NaCl(001) with unit mesh parameters 4.52 Å × 6.71 Å. The unit mesh parameters (with the exception of low coverage CH3Br/NaCl) are very similar to the lattice parameters of the a-b [or (001)] plane of bulk crystalline CH3Br at ≈153 K. By analogy with the bulk crystal, it is likely that there are two molecules per unit mesh and that the CH3 Br dipoles are nearly perpendicular to the surface and antiferroelectrically ordered. Our results suggest that the unit mesh for the low coverage phase of CH3Br/NaCl contains four molecules and that the molecular axes are parallel to the substrate surface. The implications of these results for photodissociation studies of physisorbed CH3Br are briefly discussed.

Original languageEnglish (US)
Pages (from-to)9212-9220
Number of pages9
JournalThe Journal of Chemical Physics
Volume96
Issue number12
StatePublished - 1992
Externally publishedYes

Fingerprint

Helium
mesh
Diffraction
helium
Photodissociation
Molecules
diffraction
Lattice constants
Crystalline materials
Crystals
energy
Substrates
photodissociation
molecules
lattice parameters
dipoles

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Robinson, G. N., Camillone, N., Rowntree, P. A., Liu, G., Wang, J., & Scoles, G. (1992). Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces. The Journal of Chemical Physics, 96(12), 9212-9220.

Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces. / Robinson, Gary N.; Camillone, Nicholas; Rowntree, Paul A.; Liu, Gang-yu; Wang, Jia; Scoles, Giacinto.

In: The Journal of Chemical Physics, Vol. 96, No. 12, 1992, p. 9212-9220.

Research output: Contribution to journalArticle

Robinson, GN, Camillone, N, Rowntree, PA, Liu, G, Wang, J & Scoles, G 1992, 'Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces', The Journal of Chemical Physics, vol. 96, no. 12, pp. 9212-9220.
Robinson, Gary N. ; Camillone, Nicholas ; Rowntree, Paul A. ; Liu, Gang-yu ; Wang, Jia ; Scoles, Giacinto. / Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces. In: The Journal of Chemical Physics. 1992 ; Vol. 96, No. 12. pp. 9212-9220.
@article{5d854996d0134337bdb7ee243da67201,
title = "Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces",
abstract = "Low energy helium diffraction has been used to determine the unit mesh parameters of overlayers of CH3Br physisorbed on C(0001), NaCl(001), and LiF(001) at ≈35 K. CH3Br forms a uniaxially commensurate overlayer on C(0001) with unit mesh parameters 4.26 {\AA} × 6.75 {\AA}. On NaCl(001), CH3Br forms a high coverage and a low coverage phase. The high coverage phase is incommensurate and has unit mesh parameters 4.54 {\AA} × 6.73 {\AA}, whereas the low coverage phase is commensurate with a (√2 × 3√2)R 45° unit mesh. The structure of CH3Br/LiF(001) is essentially the same as that of the high coverage phase of CH3Br/NaCl(001) with unit mesh parameters 4.52 {\AA} × 6.71 {\AA}. The unit mesh parameters (with the exception of low coverage CH3Br/NaCl) are very similar to the lattice parameters of the a-b [or (001)] plane of bulk crystalline CH3Br at ≈153 K. By analogy with the bulk crystal, it is likely that there are two molecules per unit mesh and that the CH3 Br dipoles are nearly perpendicular to the surface and antiferroelectrically ordered. Our results suggest that the unit mesh for the low coverage phase of CH3Br/NaCl contains four molecules and that the molecular axes are parallel to the substrate surface. The implications of these results for photodissociation studies of physisorbed CH3Br are briefly discussed.",
author = "Robinson, {Gary N.} and Nicholas Camillone and Rowntree, {Paul A.} and Gang-yu Liu and Jia Wang and Giacinto Scoles",
year = "1992",
language = "English (US)",
volume = "96",
pages = "9212--9220",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "12",

}

TY - JOUR

T1 - Low energy helium diffraction studies of CH3Br overlayers physisorbed on C(0001), NaCl(001), and LiF(001) surfaces

AU - Robinson, Gary N.

AU - Camillone, Nicholas

AU - Rowntree, Paul A.

AU - Liu, Gang-yu

AU - Wang, Jia

AU - Scoles, Giacinto

PY - 1992

Y1 - 1992

N2 - Low energy helium diffraction has been used to determine the unit mesh parameters of overlayers of CH3Br physisorbed on C(0001), NaCl(001), and LiF(001) at ≈35 K. CH3Br forms a uniaxially commensurate overlayer on C(0001) with unit mesh parameters 4.26 Å × 6.75 Å. On NaCl(001), CH3Br forms a high coverage and a low coverage phase. The high coverage phase is incommensurate and has unit mesh parameters 4.54 Å × 6.73 Å, whereas the low coverage phase is commensurate with a (√2 × 3√2)R 45° unit mesh. The structure of CH3Br/LiF(001) is essentially the same as that of the high coverage phase of CH3Br/NaCl(001) with unit mesh parameters 4.52 Å × 6.71 Å. The unit mesh parameters (with the exception of low coverage CH3Br/NaCl) are very similar to the lattice parameters of the a-b [or (001)] plane of bulk crystalline CH3Br at ≈153 K. By analogy with the bulk crystal, it is likely that there are two molecules per unit mesh and that the CH3 Br dipoles are nearly perpendicular to the surface and antiferroelectrically ordered. Our results suggest that the unit mesh for the low coverage phase of CH3Br/NaCl contains four molecules and that the molecular axes are parallel to the substrate surface. The implications of these results for photodissociation studies of physisorbed CH3Br are briefly discussed.

AB - Low energy helium diffraction has been used to determine the unit mesh parameters of overlayers of CH3Br physisorbed on C(0001), NaCl(001), and LiF(001) at ≈35 K. CH3Br forms a uniaxially commensurate overlayer on C(0001) with unit mesh parameters 4.26 Å × 6.75 Å. On NaCl(001), CH3Br forms a high coverage and a low coverage phase. The high coverage phase is incommensurate and has unit mesh parameters 4.54 Å × 6.73 Å, whereas the low coverage phase is commensurate with a (√2 × 3√2)R 45° unit mesh. The structure of CH3Br/LiF(001) is essentially the same as that of the high coverage phase of CH3Br/NaCl(001) with unit mesh parameters 4.52 Å × 6.71 Å. The unit mesh parameters (with the exception of low coverage CH3Br/NaCl) are very similar to the lattice parameters of the a-b [or (001)] plane of bulk crystalline CH3Br at ≈153 K. By analogy with the bulk crystal, it is likely that there are two molecules per unit mesh and that the CH3 Br dipoles are nearly perpendicular to the surface and antiferroelectrically ordered. Our results suggest that the unit mesh for the low coverage phase of CH3Br/NaCl contains four molecules and that the molecular axes are parallel to the substrate surface. The implications of these results for photodissociation studies of physisorbed CH3Br are briefly discussed.

UR - http://www.scopus.com/inward/record.url?scp=0000639161&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000639161&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000639161

VL - 96

SP - 9212

EP - 9220

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 12

ER -