Chem 122 Molecular Spectroscopy Spring 2008 Professor Ronald Cohen GSI Drew Rollins

Objectives: This course will focus on modern ideas for describing the interaction of radiation and matter with an emphasis on the use spectroscopy for the study of molecular structure and dynamics and as an analytical tool for quantitative analysis. Lectures and class discussion will cover theoretical and practical considerations for thinking about spectroscopy as applied to a variety of modern scientific problems including: Molecular structure Chemical dynamics Analytical chemistry in liquids Earth’s atmosphere and climate Kinetics of biomolecules

Topics 1.Review of quantum mechanics 2. Interaction of light with molecules Classical and quantum descriptions of radiation, multipole expansions, polarizability, perturbation theory, Fermi’s Golden rule, Einstein coefficients 3. Spectroscopy and Molecular properties Vibrations and rotations, Electronic structure, selection rules and intensities, Franck-Condon principle, line broadening, 4. Group Theory 5. Special topics Earth’s atmosphere, single molecules, surface spectroscopies, fs time resolved spectroscopy

Lectures:Mondays, Wednesdays, and Fridays AM 433 Latimer Hall Web Page: Lecturer:Professor Ronald C. Cohen B45 Hildebrand Hall Office hours: Monday 3:00-4:00 Thursday 3:00-4:00 GSI:Drew Rollins B47 Hildebrand Hall Office hours: Tuesday 9:00 – 10:00 A.M. Wednesday 3:00 – 5:00 Text:Jeanne McHale: Molecular Spectroscopy Prentice-Hall, First edition Additional readings from current literature and other supplemental texts. Grading:The approximate composition of your course grade will be: 2 Projects40% Take home Midterm (March 19)20% Final Exam30% Homework10%

Projects: Both projects are to prepare a Powerpoint presentation and to turn in an accompanying 3-5 page paper. The target audience for your talks and write-up should be your classmates. Project #1. Spectroscopic Techniques: Teach the class about a state-of-the-art method for measuring absorption, fluorescence or scattering. Include an instrument diagram, assessment of detection limit, resolution and S/N. Provide a brief overview of the historical evolution of the method. Discuss type of application the method is best suited to. Limit two talks per technique on a first come basis. Sign up with Drew. (aim for a 10 minute, 7 slide talk). Presentations in class on February 27&29. Write-up due 1-week later.

Project #2. Applications of Spectroscopy Either teach the class about a molecule, cluster or solid whose structure or function was recently (within the last 3 years) elucidated using spectroscopy or about a novel quantitative measurement of the amount of a substance observed during the last 3 yrs. Discuss the molecular energy levels, geometry, and/or energy transfer kinetics. Discuss the experimental design and implementation and include an assessment of technical limits to solving the scientific question posed. Describe unanswered questions. Limit one talk on any given system. Sign up with Drew. (aim for a 15 minute 12 slide talk). Presentations on April 26 th or 27 th. Write up due by May 13 th.

Homework HW will be assigned weekly. I expect you to come to class prepared to discuss the at least 2 or 3 of the problems at the board on the due date.

Beer’s law: I= I 0 e -n  l

Absorption Fluorescence What properties of the molecule are required to interpret/predict its UV/Vis absorption spectrum? Fluorescence?

Including CI

Spectroscopy and climate

Reflected Sunlight

Earthlight Hanel et al 1971

The Earth is in near radiative balance: Equal power arriving from the sun and leaving as the earthshine

Friday QM Review