Vibrational spectra of coadsorbed CO and H on Ni(100) and Ni(111)

A298 159

Surface Science 131 (1983) 1599166 North-Holland Publishing Company

CALCULATED AUGER SENSITIVITY FACTORS EXPERIMENTAL HANDBOOK VALUES

COMPARED

TO

Susan MROCZKOWSKI Midwest

Research

Microscopy

Inc., S510 West Flon.rt Acenue,

Mdwuukee,

Wwxmsrn

532/X,

USA

and David

LICHTMAN

Ph.ysics Department and Surface Studws kee, Wisconsin 53201, USA Received

15 March

1983; accepted

Lrrhorato~v~. Umoersi~r of W~scon.wn

for publication

29 April

Mllwuukee.

M~lwau-

1983

A pseudo-first principles technique for Auger quantitation was used to calculate relative Auger yields. These yields were compared to the experimental sensitivity factors found in the Handbook ofAuger Electron Spectroscopy. In cases where pure element standards are readily available, theory agreed quite well with experiment 95% of the time. However, when pure element standards are not available, such as the lanthanide series and the light elements from Z = 7 to 12, large deviations exist. Plots of the calculated yields for 3. 5 and 10 kV primary beams are superimposed upon the Handbook sensitivity factor graphs and the reasons for the similarities and differences are discussed.

Surface Science 13 I ( 1983) 167- I78 North-Holland Publishing Company

VIBRATIONAL AND Ni(ll1)

SPECTRA

Gary E. MITCHELL Ph_ysrcul Chemrstrv USA

167

OF COADSORBED

CO AND

H ON Ni(100)

* and John L. GLAND

Department,

General Motors Research

Luboratorres,

Warren. Mlchrgan 48090,

and J.M. WHITE Department .Received

of Chemrstry, 22 December

Unioersrty oj Texus, Austrn, Texas 78712, USA 1982; accepted

for publication

29 April

19R3

High resolution electron energy loss spectra are reported for coadsorbed hydrogen and carbon monoxide on Ni( 100) and Ni( 11I). On neither surface was there any evidence for either C-H or O-H bonds. On Ni(ll1) one CO stretching frequency is observed and it does not change significantly in the presence of coadsorbed hydrogen, This is consistent with segregation of CO and H into islands. On Ni(lOO) the situation is much different; one frequency is observed in the absence of H(a) while three CO stretching frequencies are observed for the coadsorbed layers. These are attributed to on-top, two-fold bridged and four-fold binding of CO to the Ni(lO0) surface. These results demonstrate significant structure sensitivity for the orgamzation of these coadsorbed species.