A detailed analysis of the Raman enhancement mechanisms associated with the interaction of a Raman scatterer with a resonant metal cluster

Results for Lin-H2

Prabhat K K Pandey, George C Schatz

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The results of time dependent Hartree-Fock calculations of frequency dependent polarizability derivatives for H2-Lin clusters (n=2, 4, 6) are presented and analyzed in terms of Raman enhancement mechanisms associated with interaction between H2 and the metal clusters. In these calculations, the width factors associated with unoccupied Hartree-Fock molecular orbitals are chosen so that the cluster polarizabilities are the same as those of bulk metal spheroids of the same size. The calculations are otherwise ab initio, and predict polarizability derivatives whose squares are enhanced by 103-104 for H2-Lin clusters at equilibrium geometries when irradiated at frequencies corresponding to metal cluster excitation energies. These enhancements were found to be reasonably independent of cluster size and vary by factors of 2-4 with H 2 adsorption location. The enhancements were found to vary as the inverse fourth power of the excited state widths, and to decrease with increasing adsorbate-metal separation with a complicated functionality which reflects the varying contributions of three different enhancement mechanisms. At relatively large separations, induced polarization effects (i.e., electromagnetic interactions) make a large contribution to the enhancement factor. This is also important near equilibrium, but also important at this location (as well as at large separations) is a mechanism which involves the modulation of the metal orbital energies by the adsorbate vibrational motions. At smaller separations, corresponding to the repulsive region of the H 2-Lin interaction potential, a third mechanism becomes dominant which involves the enhanced dipole matrix element derivatives which arise from charge transfer between adsorbate and metal. Symmetry of the electronic states giving rise to the cluster resonances was also found to influence enhancements, with the largest enhancements obtained for excited cluster states which have large overlap with the adsorbate HOMO and LUMO. Extension of these mechanistic interpretations to the description of surface enhanced Raman scattering (SERS) is considered.

Original languageEnglish
Pages (from-to)2959-2972
Number of pages14
JournalJournal of Chemical Physics
Volume80
Issue number6
Publication statusPublished - 1983

Fingerprint

metal clusters
Metals
Adsorbates
augmentation
scattering
interactions
Derivatives
metals
Magnetoelectric effects
Excitation energy
Electronic states
Molecular orbitals
Excited states
electromagnetic interactions
spheroids
Charge transfer
Raman scattering
excitation
Modulation
molecular orbitals

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

@article{c07867994a70411981f04200a8090c12,
title = "A detailed analysis of the Raman enhancement mechanisms associated with the interaction of a Raman scatterer with a resonant metal cluster: Results for Lin-H2",
abstract = "The results of time dependent Hartree-Fock calculations of frequency dependent polarizability derivatives for H2-Lin clusters (n=2, 4, 6) are presented and analyzed in terms of Raman enhancement mechanisms associated with interaction between H2 and the metal clusters. In these calculations, the width factors associated with unoccupied Hartree-Fock molecular orbitals are chosen so that the cluster polarizabilities are the same as those of bulk metal spheroids of the same size. The calculations are otherwise ab initio, and predict polarizability derivatives whose squares are enhanced by 103-104 for H2-Lin clusters at equilibrium geometries when irradiated at frequencies corresponding to metal cluster excitation energies. These enhancements were found to be reasonably independent of cluster size and vary by factors of 2-4 with H 2 adsorption location. The enhancements were found to vary as the inverse fourth power of the excited state widths, and to decrease with increasing adsorbate-metal separation with a complicated functionality which reflects the varying contributions of three different enhancement mechanisms. At relatively large separations, induced polarization effects (i.e., electromagnetic interactions) make a large contribution to the enhancement factor. This is also important near equilibrium, but also important at this location (as well as at large separations) is a mechanism which involves the modulation of the metal orbital energies by the adsorbate vibrational motions. At smaller separations, corresponding to the repulsive region of the H 2-Lin interaction potential, a third mechanism becomes dominant which involves the enhanced dipole matrix element derivatives which arise from charge transfer between adsorbate and metal. Symmetry of the electronic states giving rise to the cluster resonances was also found to influence enhancements, with the largest enhancements obtained for excited cluster states which have large overlap with the adsorbate HOMO and LUMO. Extension of these mechanistic interpretations to the description of surface enhanced Raman scattering (SERS) is considered.",
author = "Pandey, {Prabhat K K} and Schatz, {George C}",
year = "1983",
language = "English",
volume = "80",
pages = "2959--2972",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "6",

}

TY - JOUR

T1 - A detailed analysis of the Raman enhancement mechanisms associated with the interaction of a Raman scatterer with a resonant metal cluster

T2 - Results for Lin-H2

AU - Pandey, Prabhat K K

AU - Schatz, George C

PY - 1983

Y1 - 1983

N2 - The results of time dependent Hartree-Fock calculations of frequency dependent polarizability derivatives for H2-Lin clusters (n=2, 4, 6) are presented and analyzed in terms of Raman enhancement mechanisms associated with interaction between H2 and the metal clusters. In these calculations, the width factors associated with unoccupied Hartree-Fock molecular orbitals are chosen so that the cluster polarizabilities are the same as those of bulk metal spheroids of the same size. The calculations are otherwise ab initio, and predict polarizability derivatives whose squares are enhanced by 103-104 for H2-Lin clusters at equilibrium geometries when irradiated at frequencies corresponding to metal cluster excitation energies. These enhancements were found to be reasonably independent of cluster size and vary by factors of 2-4 with H 2 adsorption location. The enhancements were found to vary as the inverse fourth power of the excited state widths, and to decrease with increasing adsorbate-metal separation with a complicated functionality which reflects the varying contributions of three different enhancement mechanisms. At relatively large separations, induced polarization effects (i.e., electromagnetic interactions) make a large contribution to the enhancement factor. This is also important near equilibrium, but also important at this location (as well as at large separations) is a mechanism which involves the modulation of the metal orbital energies by the adsorbate vibrational motions. At smaller separations, corresponding to the repulsive region of the H 2-Lin interaction potential, a third mechanism becomes dominant which involves the enhanced dipole matrix element derivatives which arise from charge transfer between adsorbate and metal. Symmetry of the electronic states giving rise to the cluster resonances was also found to influence enhancements, with the largest enhancements obtained for excited cluster states which have large overlap with the adsorbate HOMO and LUMO. Extension of these mechanistic interpretations to the description of surface enhanced Raman scattering (SERS) is considered.

AB - The results of time dependent Hartree-Fock calculations of frequency dependent polarizability derivatives for H2-Lin clusters (n=2, 4, 6) are presented and analyzed in terms of Raman enhancement mechanisms associated with interaction between H2 and the metal clusters. In these calculations, the width factors associated with unoccupied Hartree-Fock molecular orbitals are chosen so that the cluster polarizabilities are the same as those of bulk metal spheroids of the same size. The calculations are otherwise ab initio, and predict polarizability derivatives whose squares are enhanced by 103-104 for H2-Lin clusters at equilibrium geometries when irradiated at frequencies corresponding to metal cluster excitation energies. These enhancements were found to be reasonably independent of cluster size and vary by factors of 2-4 with H 2 adsorption location. The enhancements were found to vary as the inverse fourth power of the excited state widths, and to decrease with increasing adsorbate-metal separation with a complicated functionality which reflects the varying contributions of three different enhancement mechanisms. At relatively large separations, induced polarization effects (i.e., electromagnetic interactions) make a large contribution to the enhancement factor. This is also important near equilibrium, but also important at this location (as well as at large separations) is a mechanism which involves the modulation of the metal orbital energies by the adsorbate vibrational motions. At smaller separations, corresponding to the repulsive region of the H 2-Lin interaction potential, a third mechanism becomes dominant which involves the enhanced dipole matrix element derivatives which arise from charge transfer between adsorbate and metal. Symmetry of the electronic states giving rise to the cluster resonances was also found to influence enhancements, with the largest enhancements obtained for excited cluster states which have large overlap with the adsorbate HOMO and LUMO. Extension of these mechanistic interpretations to the description of surface enhanced Raman scattering (SERS) is considered.

UR - http://www.scopus.com/inward/record.url?scp=36549092507&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=36549092507&partnerID=8YFLogxK

M3 - Article

VL - 80

SP - 2959

EP - 2972

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 6

ER -