In the Laboratory 1264 Journal of Chemical Education • Vol. 79 No. 10 October 2002 • JChemEd.chem.wisc.edu Developing experiments for a junior/senior undergraduate physical chemistry laboratory class can be very difficult and time consuming. Several textbooks provide excellent laboratory experiments that demonstrate important physical chemistry principles (1–3). However, the spectroscopic instrumentation needed to carry out the individual experiments may not be readily available within your department. Furthermore, the instrument may be too expensive to purchase for just one particular undergraduate laboratory experiment. To address these problems, we purchased a series of inexpensive modu- lar miniature UV–vis fiber-optic spectrometers from Ocean Optics Inc. to carry out several physical chemistry under- graduate laboratory experiments. One such instrument is the S2000 spectrometer, which can easily be configured with a personal computer (PC) to carry out absorption, emission, and Raman scattering experiments. The instruments can be purchased to cover a variety of wavelengths at various reso- lutions. Recently, these instruments were shown to be useful for an undergraduate instrumental analysis laboratory course to conduct absorption experiments (4 ). This work focuses on the versatility of the S2000 instruments to carry out ab- sorption, emission, and Raman scattering experiments in an undergraduate physical chemistry laboratory. Experimental Procedure Experimental Apparatus and Material The miniature fiber-optic S2000 spectrometers, LS-I tungsten halogen lamp, and fiber-optic cables were purchased from Ocean Optics Inc. Gas discharge tubes and a voltage power supply were purchased from Edmund Scientific. The spectro- graphs employed in this experiment were optimized for the spec- tral region of interest by selecting the appropriate grating which is installed and set at the factory. Table 1 provides the spe- cific details for each instrument. For each experimental setup, an A/D board was placed into a Dell Pentium II computer to collect the corresponding spectra. The data can be easily processed on a PC with Microsoft Excel. However, the ex- perimental data in this manuscript were processed on a Power Macintosh G3 computer utilizing the data analysis software programs Igor Pro (Wavemeterics Inc.) and Microsoft Excel. Cost-Effective Spectroscopic Instrumentation for the Physical Chemistry Laboratory W Gary A. Lorigan,* Brian M. Patterson, Andre J. Sommer, and Neil D. Danielson Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056; *lorigag@muohio.edu s c i t s i r e t c a r a h C h p a r g o r t c e p S . 1 e l b a T t n e m i r e p x E c i t s i r e t c a r a h C l a r t c e p S e v o o r G g n i t a r G / y t i s n e D ) m m / s e n i l ( e z a l B / h t g n e l e v a W m n l a r t c e p S / h t d i w d n a B m n e n i d o I a n o i t p r o s b 0 0 4 2 V U / c i h p a r g o l o H 5 7 5 – 7 6 4 n e g o r t i N e n o i s s i m 0 0 6 0 0 3 0 5 8 – 0 0 2 n a m a R 0 0 2 1 0 5 7 5 7 7 – 0 1 5 Cost-Effective Teacher edited by Harold H. Harris University of Missouri—St. Louis St. Louis, MO 63121 Setting Up the Instrumentation We have modified several undergraduate physical chem- istry laboratory experiments that are available in textbooks through the implementation of these Ocean Optics S2000 spectrometers (1–3). The theory and data analysis of the individual experiments are beyond the scope of this report. However, details are shown in the supplemental materials. W As observed in Figure 1, the Ocean Optics S2000 spectrometer is very versatile and can be easily configured with fiber-optic cables to conduct absorption, emission, and Raman scattering experiments. Figure 1A is a schematic of the laboratory setup for collecting experimental data in the absorption mode. The light source used in the absorption mode is a LS-I tungsten halogen lamp obtained from Ocean Optics Inc. Fiber-optic cables (Ocean Optics Inc.) are used to transfer the light from the lamp to a 10-cm path-length sample cell containing I 2 crystals and from the sample cell to the S2000 spectrometer, which is directly interfaced with an A/D board on a PC. The experimental data are stored on the PC with the Ocean Optics software. Students can save their data to disk and export it to an Excel spreadsheet for further analysis. Similarly, Figure 1B shows the instrumental setup for an emission laboratory experiment. Gas discharge tubes contain- ing either hydrogen, mercury, or nitrogen are placed into a standard 115-V SP200 power supply. A fiber-optic cable is coupled to a collimating lens and placed approximately 2 cm from the discharge tube. The fiber-optic cable is then connected to the S2000 spectrometer (which is directly connected to the PC) to collect the data. The emission spectra are gathered in the dark to minimize the effects of stray or scattered light. Finally, Figure 1C displays the configuration for collecting Raman scattering data with the S2000 spectrometer. A 35-mW He–Ne laser (Uniphase) serves as the excitation source and is directed into a holographic notch filter (Kaiser Electro– Optics), which serves as a beam splitter. Light reflected by the beam splitter (BS) is focused onto the sample using a 40× (0.65 numerical aperture) objective (Edmund Scientific). The sample, either a liquid or a solid, is placed inside a capillary tube and mounted into a sample holder (S). The Raman-scat- tered radiation is collected 180° to the incident light using the same objective and transmitted through the beam splitter and a second holographic notch filter (RF). The beam splitter and the second holographic notch filter serve to reject the elastically (Rayleigh) scattered light. Light passing through the second holographic notch filter is then focused on the entrance slit of the spectrograph using a plano-convex lens (15-mm diameter, 40-mm focal length) (Edmund Scientific). The entire setup is mounted on an optical bread board (TMC Manufacturing) using micro-positioners (Newport Corporation). The open