Knowing the geometrical structure of the molecules around us is one of the most important and fundamental issues in the field of chemistry. This course introduces the two primary methods used to determine the geometrical structure of molecules: molecular spectroscopy and gas electron diffraction.
In molecular spectroscopy, molecules are irradiated with light or electric waves to reveal rich information, including:
- Motions of electrons within a molecule (Week 1),
- Vibrational motions of the nuclei within a molecule (Week 2), and
- Rotational motions of a molecule (Week 3).
In the gas electron diffraction method, molecules are irradiated with an accelerated electron beam. As the beam is scattered by the nuclei within the molecule, the scattered waves interfere with each other to generate a diffraction pattern. In week 4, we study the fundamental mechanism of electron scattering and how the resulting diffraction images reveal the geometrical structure of molecules.
By the end of the course, you will be able to understand molecular vibration plays an important role in determining the geometrical structure of molecules and gain a fuller understanding of molecular structure from the information obtained by the two methodologies.
Week 1: Absorption and Emission of Light by Molecules *(mm:ss) indicates the time for video lectures.
- Origin of Colors (5:25)
- Color of Light, Energy of Light (5:53)
- Conjugation and Absorption (5:36)
- A Particle in a Box (9:00)
- Example: Carotene (5:29)
- A Particle on a Ring (9:30)
- Indicators (4:37)
- Emission of Light (5:08)
Week 2: Molecular Vibration
- Absorption of Infrared Light (6:10)
- Quantum Formulation of Molecular Vibration (5:20)
- Examples of Molecular Vibration (5:50)
- Anharmonicity (4:03)
- Normal Modes in 1D (3:14)
- Normal Modes in 3D (4:20)
- Inversion and Puckering (15:17)
- Electronic, Vibration and Rotation Excitation (3:36)
Week 3: Molecular Rotation
- Emission of Microwaves (5:21)
- Quantum Formulation of Molecular Rotation (5:23)
- Example of Molecular Rotation (3:59)
- Isotope Substitution (2:56)
- Angular Momentum (4:27)
- Classification of Molecules (3:40)
- Energy Diagram for Molecular Rotation (6:09)
- Vibration-Rotation Transition (8:10)
Week 4: Electron Diffraction
- Overview of Electron Diffraction (5:06)
- Electron Scattering from Single Atom (4:40)
- Electron Scattering from Diatomic Molecules (3:54)
- Effect of Molecular Vibration (3:02)
- Phase Shift (3:11)
- Electron Scattering from Polyatomic Molecules (5:44)
- Determination of Molecular Structures (5:24)
- Quantum Mechanics of Molecular Structures (1:39)
This course consists of the following:
- Lectures: Each week of the course, approx. 1h lecture videos divided into short video clips are provided. You can find the weekly themes in the course syllabus.
- After-video Quizzes: You are sometimes expected to answer these quizzes which will be graded.
- Weekly Quizzes: Each week quizzes will be provided and graded.
- Discussion Forums: Discussion forums are great tools to learn from one another. Please post your questions and thoughts, and exchange opinions with your peers. It is highly recommended that you contribute to and learn from the forums.
Upon completion of the course, you will be able to:
- explain two major methods to determine the geometrical structure of molecules in the gas phase: molecular spectroscopy and gas electron diffraction.
- quantize various motions of molecules, derive the quantized energy levels, and determine the geometrical structure of molecules from the spectrum.
- identify the fundamental mechanism of electron scattering on the basis of quantum mechanics and determine the geometrical structure of molecules from gas electron diffraction images.