The intensities of the intramolecular vibrational modes obtained by
electron energy loss spectroscopy (EELS) for CO adsorbed in top and
bridge sites on Pt(111) are presented as a function of coverage and
temperature. The top site is predominantly occupied at low coverages.
A well ordered half top�half bridge structure is formed with a c(4�2)
low-energy electron diffraction (LEED) pattern following adsorption
of 0.5 monolayers (ML) at 95 K. The ratio of the EELS cross section
of the C�O stretch in the top site to that in the bridge site is
found to be sigmat/ sigmab =1.8�0.2. The occupations of bridge and
top sites are observed to vary reversibly during temperature programmed
EELS (TP-EELS) when the temperature is linearly ramped up from 95
K to just below the onset of desorption and back down for coverages
from 0.09 to 0.44 ML; the difference in the adsorption enthalpy between
top and bridge sites is found to vary with coverage from DeltaH=0.62�0.05
kcal mol-1 at 0.09 ML to -0.14�0.05 kcal mol-1 at 0.44 ML, and returns
to near zero (-0.03�0.05 kcal mol-1) at 0.50 ML. The ratio of the
preexponential factors for site change is nub-->t/ nut-->b =2.0�0.3.
The utility of modulating the EEL spectrometer lens potentials to
minimize the effects of changes in surface order and work function
changes on the observed normalized loss intensities is investigated
and discussed. The possible effects of the low frequency frustrated
translational and rotational vibrations on the measurement of the
enthalpy difference derived from the EELS intensities are examined.
%0 Journal Article
%1 Mieher1989
%A Mieher, W. D.
%A Whitman, L. J.
%A Ho, W.
%D 1989
%I AIP
%J J. Chem. Phys.
%K ADSORPTION; CARBON CO; EEL FORCES; INTERACTIONS; INTERMOLECULAR MONOXIDE; OVERLAYERS; PLATINUM; PROPERTIES; Pt(111) REACTIONS; SORPTIVE SPECTROSCOPY; STATES; SURFACE VIBRATIONAL
%N 5
%P 3228-3239
%R 10.1063/1.456944
%T A time resolved electron energy loss spectroscopy study of CO on
Pt(111): Adsorption site occupations versus coverage and temperature
%U http://link.aip.org/link/?JCP/91/3228/1
%V 91
%X The intensities of the intramolecular vibrational modes obtained by
electron energy loss spectroscopy (EELS) for CO adsorbed in top and
bridge sites on Pt(111) are presented as a function of coverage and
temperature. The top site is predominantly occupied at low coverages.
A well ordered half top�half bridge structure is formed with a c(4�2)
low-energy electron diffraction (LEED) pattern following adsorption
of 0.5 monolayers (ML) at 95 K. The ratio of the EELS cross section
of the C�O stretch in the top site to that in the bridge site is
found to be sigmat/ sigmab =1.8�0.2. The occupations of bridge and
top sites are observed to vary reversibly during temperature programmed
EELS (TP-EELS) when the temperature is linearly ramped up from 95
K to just below the onset of desorption and back down for coverages
from 0.09 to 0.44 ML; the difference in the adsorption enthalpy between
top and bridge sites is found to vary with coverage from DeltaH=0.62�0.05
kcal mol-1 at 0.09 ML to -0.14�0.05 kcal mol-1 at 0.44 ML, and returns
to near zero (-0.03�0.05 kcal mol-1) at 0.50 ML. The ratio of the
preexponential factors for site change is nub-->t/ nut-->b =2.0�0.3.
The utility of modulating the EEL spectrometer lens potentials to
minimize the effects of changes in surface order and work function
changes on the observed normalized loss intensities is investigated
and discussed. The possible effects of the low frequency frustrated
translational and rotational vibrations on the measurement of the
enthalpy difference derived from the EELS intensities are examined.
@article{Mieher1989,
abstract = {The intensities of the intramolecular vibrational modes obtained by
electron energy loss spectroscopy (EELS) for CO adsorbed in top and
bridge sites on Pt(111) are presented as a function of coverage and
temperature. The top site is predominantly occupied at low coverages.
A well ordered half top�half bridge structure is formed with a c(4�2)
low-energy electron diffraction (LEED) pattern following adsorption
of 0.5 monolayers (ML) at 95 K. The ratio of the EELS cross section
of the C�O stretch in the top site to that in the bridge site is
found to be sigmat/ sigmab =1.8�0.2. The occupations of bridge and
top sites are observed to vary reversibly during temperature programmed
EELS (TP-EELS) when the temperature is linearly ramped up from 95
K to just below the onset of desorption and back down for coverages
from 0.09 to 0.44 ML; the difference in the adsorption enthalpy between
top and bridge sites is found to vary with coverage from DeltaH=0.62�0.05
kcal mol-1 at 0.09 ML to -0.14�0.05 kcal mol-1 at 0.44 ML, and returns
to near zero (-0.03�0.05 kcal mol-1) at 0.50 ML. The ratio of the
preexponential factors for site change is nub-->t/ nut-->b =2.0�0.3.
The utility of modulating the EEL spectrometer lens potentials to
minimize the effects of changes in surface order and work function
changes on the observed normalized loss intensities is investigated
and discussed. The possible effects of the low frequency frustrated
translational and rotational vibrations on the measurement of the
enthalpy difference derived from the EELS intensities are examined.},
added-at = {2009-10-30T10:04:05.000+0100},
author = {Mieher, W. D. and Whitman, L. J. and Ho, W.},
biburl = {https://www.bibsonomy.org/bibtex/2eabda29cd2078e6bbea98e94f5d57657/jfischer},
doi = {10.1063/1.456944},
interhash = {bdcfc4a5ddb9c184dc315f5601a37e41},
intrahash = {eabda29cd2078e6bbea98e94f5d57657},
journal = {J. Chem. Phys.},
keywords = {ADSORPTION; CARBON CO; EEL FORCES; INTERACTIONS; INTERMOLECULAR MONOXIDE; OVERLAYERS; PLATINUM; PROPERTIES; Pt(111) REACTIONS; SORPTIVE SPECTROSCOPY; STATES; SURFACE VIBRATIONAL},
number = 5,
pages = {3228-3239},
publisher = {AIP},
timestamp = {2009-10-30T10:04:17.000+0100},
title = {A time resolved electron energy loss spectroscopy study of CO on
Pt(111): Adsorption site occupations versus coverage and temperature},
url = {http://link.aip.org/link/?JCP/91/3228/1},
volume = 91,
year = 1989
}