First principles determination of the formaldehyde photoelectron spectrum: A physical chemistry laboratory

CHED 1800

Evan L. Millam, emillam@usi.edu1, Richard Lord, rllord@indiana.edu2, Lisa Davis, Susan M. E. Green, Eric Brown, Chad Offerman, and Paul Wray. (1) Department of Chemistry, University of Southern Indiana, 8600 University Boulevard, Evansville, IN 47712, (2) Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, IN 47405
A first principles determination of the formaldehyde photoelectron spectrum is presented as a laboratory accessible to an undergraduate physical chemistry course. The robustness and user-friendliness of software developed for the Franck-Condon factor calculation are shown. While the calculator is suitable for determining multiple types of electronic spectra, the presentation is focused upon the formaldehyde example. Since it is based upon ionization, photoelectron spectroscopy is an intuitively satisfying electronic technique that offers undergraduate students a glimpse into abstract and often confusing concepts such as electronic configuration and vibrational structure. While experimental application of this method is both expensive and challenging, it is ideally suited to theoretical determination. The relative complexity of the formaldehyde spectrum enables a through discussion of spectroscopic assignment. The unique pedagogical advantages of the laboratory are discussed.