Related Experiment Video
Updated: Jul 12, 2026

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
Published on: August 5, 2016
Valence electron orbitals of an oligo(p-phenylene-ethynylene)thiol on gold
Christopher D Zangmeister1, Steven W Robey, Roger D van Zee
1National Institute of Standards & Technology, Gaithersburg, Maryland 20899, USA. christopher.zangmeister@nist.gov
Abstract:
This communication reports measurement of one-photon (21.2 eV) and one-color, two-photon (3.2-4.5 eV) photoemission spectra of 4,4'-bis-(phenylethynyl)benzenethiol chemisorbed on gold. Four features are observed in these spectra: two occupied, predominantly molecular levels below the Fermi level and two unoccupied, predominantly molecular levels above the Fermi level. The occupied and unoccupied bands closest to the Fermi level are assigned to delocalized pi-bands, and the other occupied and unoccupied bands, to localized pi-bands. With this assignment, the hole- and electron-injection barriers and the transport gap for those levels are deduced.
Related Concept Videos
Organic Compounds
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Inductive Effects on Chemical Shift: Overview
π Molecular Orbitals of 1,3-Butadiene
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
Basicity of Heterocyclic Aromatic Amines
Physical Properties of Carboxylic Acid Derivatives
Among the carboxylic acid derivatives, the boiling points of acid chlorides and esters are very similar and are the lowest in the series. Acid anhydrides have slightly higher boiling...

