NSF Award
9952604
Chemistry (12) Ultrashort laser pulse-based experiments have become ubiquitous in experimental physical chemistry. In order for students to understand recent developments and obtain "hands on" experience with such techniques, access to a pulsed laser-based system with pump-probe capability for luminescence studies is important. In this project, the instrumentation to do this is being incorporated into the undergraduate physical chemistry laboratory curriculum. The system consists of a Q-Switched YAG laser with harmonic generation in either the near-UV (355 nm) or mid-UV (266 nm) with a 3 ns (4-8 mJ) pulse, thus providing excitation in a variety of molecules. The fast luminescence is detected by a sensitive PIN photodiode detector with 400 ps response and digitized by an ultrahigh bandwidth (1 GHz) digital oscilloscope. The YAG laser is also used to pump an existing tunable dye laser, whose probe output is temporally delayed from 0 to 50 ns using an inexpensive and novel optical delay line based on a toy train track and engine. A set of experiments for the undergraduate physical chemistry laboratory that measure fluorescence lifetimes of a series of aromatic hydrocarbons and also directly monitor intersystem crossing processes on the nanosecond time scale using optically delayed triplet- triplet absorption are being adapted and implemented, with enhancements. The adapted materials come from both the chemical education literature (J. Chemical Education) and from the research literature. The laser equipment is also being introduced into inorganic, organic and advanced organic courses, courses not normally associated with laser chemistry. This considerably broadens the impact of this project. Evaluation and assessment activities are being assisted by an external evaluator, experienced in laser chemistry, and by a chemical education specialist. The results will be disseminated through dedicated Web pages and papers submitted to the Journal of Chemical Education.
