Lasers in Chemistry A New Elective Laboratory Course Karen I. peterson' and R. Ken ~ o r c e ~ University of Rhode Island, Kingston, R I 02881 Laser spectroscopy i s a technique t h a t h a s been essent i a l l y neglected in t h e c u r r i c u l u m hut w h i c h h a s widespread use in t h e sciences. In order t o b e able t o conduct laser spectroscopy experiments in a knowledgable way, one needs t o k n o w basic ootics a n d data-collection methods as w e l l as have a basic understanding of components such as lasers a n d monochromators. We have d e v e l o ~ e da n elect i v e laboratory course, "Lasers in Chemistry", t o fillt h i s need. O u r first task in developing t h e course was t o design a n d b u i l d a complete undergraduate laser laboratory in w h i c h a student w o u l d h e able t o conduct a wide variety of optical a n d spectroscopic experiments. T h e m a j o r e q u i p m e n t items are l i s t e d in Table 1 along w i t h t h e manufacturer a n d 1991-1992 price. N o t included in t h i s l i s t are items
Table 1. List of Major Equipment Items Item Nn-pumped dye laser Argon ion laser
lh meter monochromator 0.2 meter monochromator 100 MHz oscilloscope Gated integratorboxcar integrator system Computer, IBM-AT HeINe lasers Picoammeter HV supplies NIM bin Digital power meters Rotary stage Breadboards
ManufacturerIModel Laser Photonics/LNIOOC2 Ion Laser Tech15490A Aries15001S-SM Instruments SAIHQO TeMronixl2245A Stanford Researchl250,245,270 Gateway20001286 VGA Edmund Scientific Aerotech Keithleyl485 Mechtronicsl255 Mechtronicsll52 Newport Corpl815-SL Edmund Sci/A34,515
Newport Corpl481 Edmund Scientific/R38,434 R38.433 PMT housings Products for ResearchIl402RF Chart recorder Kipp & ZonenBD-41 Holographic edge Physical Optics filter Corp/RHE514.1 D Photomultiplier HamamatsulR928 tubes /PI28 Beam expander Oriel Corp115900 Photodiode detector ThorlabsIDETPSI Printer
such as optics, optical mounts, translation stages, sample cells, electrical connectors, a n d other items t h a t cost less t h a n a f e w hundered dollars. So far, w e have found t h e equipment t o b e reliable. The laboratory course i s t w o credits a n d meets once a week for four hours. The laboratory can accommodate u p to eight o r n i n e students per section. The general structure of a class session i s t o s t a r t with a lecture l a s t i n g about one h o u r a n d t h e n divide t h e students i n t o groups of t w o o r t h r e e t o conduct t h e experiments. Since m a n y experiments, p a r t i c u l a r l y a t t h e b e g i n n i n g o f t h e course, a r e short, t w o o r three can b e finished in a day. R a t h e r t h a n 'Present address: Department of Chemistry, San Diego State University, San Diego, CA 92182-1030 2~eceased.
Cost
Table 2. Course Outline and Experlments
$9,015
ootics A. Basic properties of.lenses B. Construction of a beam expander C. Measurement of polarization by a filter D. Brewster angle and index of refraction Introduction to Lasers II. E. Measurement of beam spot size and divergencea F. Double slits diffractiona G. Simple dye laser H. Bandwidth of a dye laser Components of Data Collection 111. I. Characteristics of a grating J. Measurement of a mercuj lamp spectrum K. Rise and fall times of PMT and a photodiode: relative delay L. PMT response curve Introduction to Laser Fluorescence Spectroscopy IV. M. Chlorophyll fluorescence N. Measurement of the output of a N2 dye laser 0.12 fluorescenceb Pulsed Fluorescence Spectroscopy v. P. Use of a boxcar averagerlgate integrator Q. Pyrene time-resolved fluorescence Chemistry with Lasers VI. R. Bimoiecular quenching kineticsC S. Diffusion of ions in aqueous solutiond Raman Spectroscopy VII. T. Raman spectrum of CC14 U. Signal enhancement with a lock-in amplifier VII, Independent Projects 'Adapted from Ref. 2. There are many sources for this experiment; we used a very simplified version of that described in Ref. 3. 'Adapted from Ref. 4. I.
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have the students write reports, we quiz them every week on information they should have included in their notebook. The course, a n outline of which is given in Table 2, is organized into seven major topics and a n independent study project. The first nine weeks were taken up with these tonics. The last four weeks were devoted to independentbrojects. We supplied a list of ideas for these proiects. but some students came UD with their own ideas. " eeneral resnonse from the students has been enthusiastic:~ritten c&se evaluations from the students sug-eest to us that the overall structure of the course is appropriate. We found that some of the initial e ~ p e r i m e n t s , ~ ~ u c h d~,uhleahts d~lfraction,appeared to be inelfective while the later spertroscopy experiments were appreciated greatly bur not tmtirely understood. Therefore, in the future we orohablv will redure the time went on the first two sectionslthat now take up four weeks time and increase the
he
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Journal of Chemical Education
time for sections N-VIII. Copies of our laboratory handbook are available from the author (KIP)upon request. Acknowledgment We would like to thank the NSF for funds to purchase equipment for the laser spectroscopy laboratory under the auspices of the ILI program, Grant no. CHE-9051600.We also would like to thank the University of Rhode Island for its matching funds contribution. Literature Cited 1. Ditzler, M. A.Department of Chemistm College ofthe Holy Cmss. personal commu-
nication. 1992.
1985.
2. Simhi, R. S. A C o u i s ofEzprtimenis luilh HeNeLczsw: Wiley: New York, 3. Shoemaksr, D. P; Garland, C. W;Nibler. J. W. Experiments in Ph-1 Chomislry,
5th ed.: Mdjraw-Hill: New York, 1989. 4. Demab. J.N. J. Chom. Edue 1976.53,657-663. 5. King, M. E.;Pitha, R. W.; Sontun, S. F J. Chrm Edvc 1988.66.787-790.
