Symmetry analysis of angle-resolved photoemission: Polarization dependence and lateral interactions in chemisorbed benzene

• Published in: Surface science Vol. 85; no. 2; pp. 335 - 352
• Main Authors: Nyberg, Graeme L., Richardson, Neville V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.1979
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(79)90257-7

Using an oriented free-molecule model, exact selection rules are used to determine which bands are allowed in both normal and off-normal emission as a function of polarization direction. An approximate angular analysis of the final states is then applied to give a qualitative account of the emission angle dependence. The consequences of both inter- and intra-ad sorbate unit cell lateral interactions are considered, with effects which are new to adsorbate photoemission. When applied to benzene-on-Pd(100) angle-resolved spectra these concepts are shown to give a very adequate description of the results. Previous assignments are confirmed with the exception that the second π-orbital is now located on the leading edge of the C-band, thus implying that both π-orbitals are subject to similar adsorbate-substrate binding shifts. In conjunction with LEED data a specific adsorbate geometry is proposed.