Methods for Determining the Infrared Complex Refractive Indices N(Λ) and K(Λ) from Organic Solid Powders: Comparison of a Sucrose Single Crystal and a Pressed Pellet

Author

Michael O. Yokosuk
Danielle L. Saunders
Charles Tom Resch
Jeremy D. Erickson
Charmayne E. Lonergan, Missouri University of Science and TechnologyFollow
Sarah D. Burton
Mark E. Bowden
Kelly A. Peterson
Timothy J. Johnson
Tanya L. Myers

Abstract

There exists a need to measure optical constants n and k for many materials, especially organic solids in the infrared spectral region, but at present, there are only two established methods for making such measurements: single-angle (SA) reflectance and infrared spectroscopic ellipsometry (IRSE). the former derives the n/k vectors via measurement of the change in the amplitude of light reflected from the sample and then uses the Kramers-Kronig transform, while the latter measures the change in polarization of the reflected light from the sample to derive n/k. Here we make a direct comparison between the n/k vectors derived from SA measurements of a sucrose single crystal and the n/k values obtained after the crystal had been crushed, ground to powder, and pressed into a pellet form. the pellet was measured not only by SA but also via the IRSE method, and we found that pressing specular-quality pellets was critical, especially for the SA data. the n/k values of this typical organic molecule all agree to within 0.04 root-mean-square error, confirming that a pressed pellet can be used instead of a crystal to derive the intrinsic n/k vectors. This result is important for the many organic materials that, unlike sugar, do not have centimeter-sized crystals readily available.

Recommended Citation

M. O. Yokosuk and D. L. Saunders and C. T. Resch and J. D. Erickson and C. E. Lonergan and S. D. Burton and M. E. Bowden and K. A. Peterson and T. J. Johnson and T. L. Myers, "Methods for Determining the Infrared Complex Refractive Indices N(Λ) and K(Λ) from Organic Solid Powders: Comparison of a Sucrose Single Crystal and a Pressed Pellet," ACS Applied Optical Materials, vol. 1, no. 1, pp. 41 - 47, American Chemical Society, Jan 2023.

The definitive version is available at https://doi.org/10.1021/acsaom.2c00004

Department(s)

Materials Science and Engineering

Comments

U.S. Department of Energy, Grant DE-AC05-76RL01830

Keywords and Phrases

extinction coefficient; optical constants; pressed pellet; refractive index; single crystal; single-angle reflectance; spectroscopic ellipsometry; sucrose

International Standard Serial Number (ISSN)

2771-9855

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 American Chemical Society, All rights reserved.

Publication Date

27 Jan 2023