TRANSMITTANCE % 90°4, o°{[ 4000 t 3500 3000 2500 i} 2000 1800 These spectra, of a piece of rolled polyester film only 1.5 mm square, were taken with the aid of two P-E accessories: a wire-grid polarizer and a | X 4 refracting beam condenser (see illustration). They show how polarized radiation can be used to obtain fundamental information on even the smallest polymer samples. From the dichroic behavior of two absorption bands, it can be seen that the polymer chains ore preferentially aligned parallel to the machine, or rolling direction. Here's how: the two spectra were taken with the wire grid polarizer at orientations 90° HERE'S A NEW DIMENSION IN MICROANALYSIS Our Model 62171IR Spectraphotometer lets you work with the smallest of samples. You can record good spectra with less than 0.1 micro- liter of liquid—or even as little as 50 nanograms of solid. The unique. micro-capabilities of the Model 621 result from its fast £/4.5 optical system, folded, compact optical path and small sample aperture. We use aspheric optics for the most t 1600 1400 FREQUENCY cm"! | 1200 1000 | 800 600 400 200 apart. The relative intensities of the C=O band at 1725 cm-! and the aromatic carbon-hydrogen bending vibration at 1500 cm-! can be used to determine the relative orientations of the transition moments associated with these vibrations. The 1725 em! band has its maximum intensity when the polarizer is oriented to transmit radiation perpendicular to the machine direction of the film: i.e., the band exhibits perpendicular dichroism. On the other hand, the 1500 cm-? band shows parallel dichroism. The Model 621 makes this kind of analysis easy to do. efficient transfer of enargy and precise imag- ery. The shorter optical path makesit easier to purge water vapor and carbon dioxide from the sealed instrument. We've designed special accessories to give you optimum micro-performance. We offer a microcell and beam-condenser combination, an ultra-micro 6X beam condenser, and a micro- specular reflectance attachment. The spectra show how a new Perkin-Elmer accessory, the Wire Grid Polarizer, is used in conjunction with a beam condenser to reveal orientation of the functional groups in a polyester film. The unique power of this instrument in the micro-sampling range also makes it ideal for analyzing chromatographic fractions. But it hasn‘t been designed for microanalysis alone. We've built in every possible convenience and technical improvement for rapid, precise work. You can alsa handle ordinary samples faster and easier. The Model 621 gives you unparalleled sensitivity over its entire range. Write for our 16-page brochure on the Model 621. We’ll also send you a brochure describing the many accessories available. Address: Instrument Division, Perkin-Elmer Corporation, Main Avenue, Norwalk, Conn. 06852. 723 PERKIN-ELMER Detail of sample area showing 1x4 beam condenser (foreground) and attenuator mounted in reference beam.