Molecular Spectroscopy – CHEM 5591 Spring 2019 J. Mathias Weber

Technicalities(1) Requirements: two semesters of undergraduate physical chemistry and graduate standing recommended: firm grasp of algebra, complex numbers, calculus, differential equations, CHEM 5581 Class hours: MWF 09:00 am to 09:50 am Office Hours: Wednesday, Thursday 5 pm – 6 pm DOES THIS WORK FOR EVERYONE?

Technicalities(2) Locations: JILA tower A709 phone 492-7841 email weberjm@jila.colorado.edu web site: http://jila.colorado.edu/weberlabs/course-CHEM5591.html Exam schedule: Two-hour exams: Feb 26, April 9, 6-8 pm, EKLC E1B75 Final Exam: date, time, and location TBA

Proposed: Thursday nights, 6 – 7 pm. Technicalities(3) Problem sets (homework): usually handed out (i.e. posted on course web site) on Fridays, to be returned the following Fridays before class homework will be graded by graduate student Wyatt Zagorec-Marks. credits accumulated over the semester determine your homework performance grade. Everyone may drop one homework assignment without penalty. worked solutions to problem sets will be posted on the course web page. Travel: Due to professional travel, there will be no class meetings on Feb. 18, Feb. 20, and Feb. 22, as well as on April 1, April 3, and April 5. The missed lectures will be given on other dates instead. There may be other travel coming up. Proposed: Thursday nights, 6 – 7 pm.

Technicalities(4) Grades: homework performance: 40% clicker questions (participation) 5% average of the two-hour-exams: 30% final exam: 25% All slides and clicker questions will be posted on the course web page Literature: Wolfgang Demtröder “Molecular Physics” (main text book for the course). Wolfgang Demtröder “Laser Spectroscopy” (useful resource) H. Haken, H. C. Wolf “Molecular Physics and Elements of Quantum Chemistry” (useful resource) G. Herzberg “Molecular Spectra & Molecular Structure” (the spectroscopy “bible”) Browse the library or the book store for other books that you may like...

Tentative List of Topics Classical treatment of interaction of light and matter Transitions between states - Einstein coefficients Line shapes States and Spectra of the H-Atom States and Spectra of Multielectron Atoms Orbit and Spin Magnetism, Spin-Orbit Interaction, Fine Structure The Born-Oppenheimer Approximation Purely Rotational Spectra of Diatomic Molecules Ro-vibrational Spectra of Diatomic Molecules Electronic States of Diatomic Molecules Electronic Spectra of Diatomic Molecules Multiphoton transitions Raman Spectroscopy Nuclear Spin Statistics Group Theory Rotations of Polyatomic Molecules Vibrations of Polyatomic Molecules – Normal Modes Electronic States of Polyatomic Molecules Spectra of Polyatomic Molecules Spectra of Nanomaterials Semiclassical description of an absorption process Lasers

Goals of Spectroscopy: Experimental determination of the properties of the quantum states of a system (atoms/molecules/materials). Theoretical prediction of these properties. Study of transition probabilities between these states Understanding of dynamics and processes (e.g. dissociation, radiationless transitions, excited state lifetimes, electron emission, ...)

Approaches: How do we get such data? Interaction of a sample with Light: absorption emission scattering Matter particles electrons neutrons atoms molecules ...

Method typical spectral range degree of freedom NMR 107 – 109 Hz 3·10-4 – 3·10-2 cm-1 nuclear spin EPR 109 – 1011 Hz 3·10-2 – 3 cm-1 electron spin microwave spectroscopy 109 – 1012 Hz 3·10-2 – 30 cm-1 mol. rotation infrared spectroscopy 1012 – 1014 Hz 30 – 3·103 cm-1 mol. vibrations UV/vis spectroscopy 1014 – 1016 Hz 3·103 – 3·105 cm-1 valence electrons X-ray spectroscopy > 1016 Hz > 3·105 cm-1 core electrons

Typical energies: ionization potentials 5 – 15 eV (40 – 121·103 cm-1) electron affinities 0 – 4 eV (0 – 32·103 cm-1) dissociation energies 1 – 5 eV (0 – 40·103 cm-1) vibrations (fundamental) 0.01 - 0.5 eV (80 – 4000 cm-1) rotations < 1 meV (0.008 – 8 cm-1)   Outlier: H2 (Be = 60.853 cm-1; e = 4401.21 cm-1)

The color of a nonfluorescent object is due to the light left after absorption

The color of a nonfluorescent object is due to the light left after absorption absorbed perceived perceived absorbed absorbed perceived