title: Experimental and theoretical study of rotationally inelastic diffraction of H2(D2) from methyl-terminated Si(111).
abstract: Fundamental details concerning the interaction between H2 and CH3-Si(111) have been elucidated by the combination of diffractive scattering experiments and electronic structure and scattering calculations. Rotationally inelastic diffraction (RID) of H2 and D2 from this model hydrocarbon-decorated semiconductor interface has been confirmed for the first time via both time-of-flight and diffraction measurements, with modest j = 0 → 2 RID intensities for H2 compared to the strong RID features observed for D2 over a large range of kinematic scattering conditions along two high-symmetry azimuthal directions. The Debye-Waller model was applied to the thermal attenuation of diffraction peaks, allowing for precise determination of the RID probabilities by accounting for incoherent motion of the CH3-Si(111) surface atoms. The probabilities of rotationally inelastic diffraction of H2 and D2 have been quantitatively evaluated as a function of beam energy and scattering angle, and have been compared with complementary electronic structure and scattering calculations to provide insight into the interaction potential between H2 (D2) and hence the surface charge density distribution. Specifically, a six-dimensional potential energy surface (PES), describing the electronic structure of the H2(D2)/CH3-Si(111) system, has been computed based on interpolation of density functional theory energies. Quantum and classical dynamics simulations have allowed for an assessment of the accuracy of the PES, and subsequently for identification of the features of the PES that serve as classical turning points. A close scrutiny of the PES reveals the highly anisotropic character of the interaction potential at these turning points. This combination of experiment and theory provides new and important details about the interaction of H2 with a hybrid organic-semiconductor interface, which can be used to further investigate energy flow in technologically relevant systems.
authors: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA.
authors: Kevin J
authors: KJ
authors: Nihill
authors: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA.
authors: Zachary M
authors: ZM
authors: Hund
authors: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors: Alberto
authors: A
authors: Muzas
authors: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors: Cristina
authors: C
authors: Díaz
authors: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors: Marcos
authors: M
authors: Del Cueto
authors: School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra ACT 2610, Australia.
authors: Terry
authors: T
authors: Frankcombe
authors: Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, Pasadena, California 91125, USA.
authors: Noah T
authors: NT
authors: Plymale
authors: Division of Chemistry and Chemical Engineering, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 210 Noyes Laboratory, 127-72, Pasadena, California 91125, USA.
authors: Nathan S
authors: NS
authors: Lewis
authors: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors: Fernando
authors: F
authors: Martín
authors: The James Franck Institute and Department of Chemistry, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA.
authors: S J
authors: SJ
authors: Sibener