Resonances in the K shell excitation spectra of benzene and pyridine: Gas phase, solid, and chemisorbed states

K shell excitation spectra of the aromatic molecules benzene and pyridine in the gas phase are compared to those for the solids (ices) and for monolayers chemisorbed on Pt(111). The gas phase and solid spectra are essentially identical and even the spectra for the chemisorbed molecules exhibit the same resonances. Because of the orientation of the molecules upon chemisorption the latter spectra show a strong polarization dependence as a function of x‐ray incidence. This polarization dependence in conjunction with a multiple scattering Xα calculation for the benzene molecule allows us to assign the origin of all K shell resonances. The resonances are found to arise from transitions to π* antibonding orbitals and to σ* shape resonances in the continuum. The shape resonances are characterized by potential barriers in high (l=5 and 6) angular momentum states of the excited photoelectron. The polarization dependence and energy position of the resonances allow the molecular orientation on the surface to be dete...

[1]  J. Stöhr,et al.  Bonding and bond lengths of chemisorbed molecules from near-edge X-ray absorption fine-structure studies , 1983 .

[2]  G. Loubriel.  Theoretical calculation of bonding, shakeup energies, and shakeup intensities in Ni(CO) 4 , 1979 .

[3]  M. Hove,et al.  Efficient Scheme for Calculation of Low-Energy Electron-Diffraction Intensities in the Presence of Large Superlattices, with Application to the Structural Analysis of Benzene Adsorbed on Rh(111) , 1983 .

[4]  Louis Noodleman.  The determination of optical absorption intensities using the Xα scattered wave method , 1976 .

[5]  M. Karplus,et al.  Application of Xα multiple-scattering theory to planar organic molecules: One-electron properties and ionization potentials of benzene, pyridine, pyrazine, pyrrole, and imidazole , 1980 .

[6]  H. Ibach,et al.  Vibration spectroscopy of benzene adsorbed on Pt(111) and Ni(111) , 1978 .

[7]  E. Cox.  Crystal Structure of Benzene , 1958 .

[8]  P. Avouris,et al.  High-resolution C 1s and O 1s core-excitation spectroscopy of chemisorbed, physisorbed, and free CO , 1984 .

[9]  F. Netzer,et al.  Electronic energy losses of ethylene and benzene adsorbed on Pt(111) , 1979 .

[10]  J. Stöhr,et al.  Absorption-edge resonances, core-hole screening, and orientation of chemisorbed molecules: CO, NO, and N 2 on Ni(100) , 1982 .

[11]  R. Howe,et al.  Chemistry and Physics of Solid Surfaces V , 1984 .

[12]  D. Kilcast,et al.  Experimental and theoretical studies of the molecular core binding energies of some six-membered ring nitrogen heterocycles and their perchloro- and perfluoro-derivatives , 1972 .

[13]  W. L. Jolly,et al.  A table of absolute core-electron binding-energies for gaseous atoms and molecules , 1980 .

[14]  W. Thiel,et al.  Shape resonances in photoionization: Correlation with STO-3G MO results☆ , 1984 .

[15]  J. Rousseau,et al.  On the vibrational electron energy loss spectra of benzene chemisorbed on the (111) and (100) nickel faces , 1979 .

[16]  H. Schaefer,et al.  Localized and Delocalized 1s Hole States of the O 2 + Molecular Ion , 1972 .

[17]  J. Davenport.  Ultraviolet Photoionization Cross Sections for N 2 and CO , 1976 .

[18]  C. E. Brion,et al.  Carbon K-shell excitation of C2H2, C2H4, C2H6 and C6H6 by 2.5 keV electron impact , 1977 .

[19]  J. Stöhr,et al.  Determination of intramolecular bond lengths in gas phase molecules from K shell shape resonances , 1984 .

[20]  F. Jellinek,et al.  Molecular symmetry and crystal structure of dibenzene chromium , 1966 .

[21]  C. E. Brion,et al.  Reference energies for inner shell electron energy-loss spectroscopy , 1984 .

[22]  Edward Teller,et al.  Electronic Spectra of Polyatomic Molecules , 1941 .

[23]  Melvin B. Robin,et al.  Higher excited states of polyatomic molecules , 1974 .

[24]  D. Dill,et al.  Molecular effects on inner‐shell photoabsorption. K‐shell spectrum of N2 , 1976 .

[25]  J. C. Slater,et al.  Self-Consistent-Field X α Cluster Method for Polyatomic Molecules and Solids , 1972 .

[26]  Allen L. Johnson,et al.  Near-edge X-ray-absorption fine-structure studies of chemisorbed hydrocarbons: bond lengths with a ruler , 1984 .

[27]  H. Kleinpoppen,et al.  Inner-shell and X-Ray physics of atoms and solids : [proceedings] , 1981 .

[28]  P. Coppens,et al.  Electronic structure of benzene chromium tricarbonyl by X-ray and neutron diffraction at 78 K , 1973 .

[29]  D. A. Shirley,et al.  The prediction of core-level binding-energy shifts from CNDO molecular orbitals☆ , 1974 .

[30]  G. L. Findley,et al.  Photophysics and Photochemistry in the Vacuum Ultraviolet , 1985 .

[31]  J. Stöhr,et al.  Carbon K‐shell electron energy loss spectra of 1‐ and 2‐butenes, trans‐1,3‐butadiene, and perfluoro‐2‐butene. Carbon–carbon bond lengths from continuum shape resonances , 1984 .