1. Photoelectron Spectroscopy
(PES)

2. Photoelectron Spectroscopy
Slide 1
Photoelectron Spectroscopy
What is PES?
Photoelectron spectroscopy analyzes the kinetic energy distribution of the emitted photoelectrons to study the composition and electronic state of a sample.
PES apparatus
iramis.cea.fr

3. Photoelectron Spectroscopy
Slide 2
How it works: 1. The sample is exposed to electromagnetic radiation (typically x-ray or UV photons) 2. Electrons jump off of the surface of a sample and go through an analyzer

4. Slide 3
Image source: Inna M Vishik

5. Kinetic Energy Analyzer
X-ray or UV
Source
Kinetic Energy Analyzer
6.26
0.52
Binding Energy (MJ/mol)
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6. Energy to remove an electron
PES Data for Neon
SLIDE 5
Each peak represents the electrons in a single sublevel in the atom
The bigger the peak , the more electrons
Electrons generally farther from the nucleus
Energy to remove an electron
“binding energy” a.k.a ionization energy
often measured in eV (electron volts)
1 eV = × 10-19 J
Electrons
generally closer to the nucleus

7. Oxygen (1s22s22p4) SLIDE 6 4 electrons in 2p 2 electrons in 2s

8. Identify the element whose PES data is shown
SLIDE 7
Identify the element whose PES data is shown
Sodium
Why is one peak much larger than the others?
This peak represents
6 electrons in the 2p
sublevel
The other peaks
represent only 1 or 2
electrons
In which orbitals are the electrons
Represented by peak A? 3s A

9. Sketch the expected PES spectrum for Aluminum
SLIDE 8

10. Hydrogen vs. Helium SLIDE 9
The helium peak is farther to the right (higher energy) thus more energy is needed to remove the 1s electrons in helium. They must be held more tightly because there is a higher effective nuclear charge. (Helium has 2 protons pulling on 1s but hydrogen only has 1)
The helium peak is twice as tall because there are twice
as many electrons in the 1s sublevel

11. Example:
SLIDE 10
oxygen
nitrogen
#e-
#e-
energy
energy
The PES data above shows only the peak for the 1s electrons. Why is the peak for Nitrogen farther to the left?
It takes less energy to remove a 1s electron from nitrogen because it has a lower effective nuclear charge (fewer protons) than oxygen

12. Portions adapted from
AP 2003 FRQ #5
Chemistry, Chang, 10th edition
APSI 2013 OU presentation; J. Beninga
Wikipedia: IR spectroscopy gifs