Abstract

Two examples of the effect of convergence on infrared spectra are presented. In the first case a sample has absorbing dipoles oriented parallel to a unique axis and randomly oriented in a plane perpendicular to that axis. The incident radiation is perpendicular to the unique axis. Such samples are shown to have slightly different dichroic ratios for convergent radiation than for parallel radiation. An error in the literature concerning this case is pointed out.

In the second case a uniaxial crystal having absorbing dipoles parallel to the unique axis is shown to absorb convergent radiation when the radiation comes toward the sample along the unique axis. This absorption which is not observed for parallel radiation may reach a maximum of 53 to 56% depending on the degree of convergence, the thickness of the sample, and the strength of the absorbing dipole. The frequency of the band observed because of the effect of convergence may also be appreciably higher than that for the allowed transition.

© 1958 Optical Society of America

Double-Beam Infrared Microspectrometer

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