Angle-resolved ultraviolet photoelectron spectroscopy of oriented film of model compound of poly( p-phenylene): wave number( k) conservation and k blurring in a system with small number of repeating units

• Published in: Journal of electron spectroscopy and related phenomena 1995-12, Vol.76, p.553-558
• Main Authors: Ishii, H., Narioka, S., Edamatsu, K., Kamiya, K., Hasegawa, S., Ohta, T., Ueno, N., Seki, K.
• Format: Article
• Language: English
• ISSN: 0368-2048; 1873-2526
• DOI: 10.1016/0368-2048(95)02516-2

The electronic structure of oriented thin films of sexiphenyl (6P) as a short model compound of poly( p-phenylene) (PPP) was investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) using synchrotron radiation. The sample film of 6P was prepared by vacuum evaporation onto a heated Ag substrate. Infrared reflection-absorption spectroscopy, x-ray diffraction, and the observed selection rules for ARUPS indicated that the 6P molecules are highly oriented aligning its molecular axis parallel to the surface normal. In the normal emission spectra of ARUPS, the band intensity of the HOMO and the next HOMO was enhanced at hv=28∼40eeV. This enhancement can be explained in terms of the wave number( k)-conservation rule in the one-dimensional intramolecular band with some initial state broadening of k (or relaxation of k-conservation rule) due to the small number of repeating units. This indicates that wave number k along the molecular axis serves as a reasonably good quantum number even in a system consisting of only six repeating units.