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ATR Prism Selection Criteria

By Carlos Morillo

January 4, 2024

Introduction

ATR method is used to analyze the sample surface within 1~2 μm in depth. The measurement is collected when the ATR prism is in contact with the sample. In ATR method, the penetration depth of light into the sample for total reflection depends on the RI of prism and sample, incidence angle and wavelength. In addition, measurement range and durability depend on the material of the prism. Features of each prism are shown as follows.

Prism	RI (n₁)	Penetration Depth dp^*1 (1000cm^-1)	RI of Sample (n₂)^*2 for Total Reflection	Measurement Limit in Low Wavenumber^*3 Range
ZnSe	2.4	~ 2.0 μm	<= 1.7	~550 cm^-1
Diamond	2.4	~ 2.0 μm	<= 1.7	~400 cm^{-1 *4}
Ge	4.0	~ 2.0 μm	<= 2.8	~650 cm^-1

Prism	Feature of Prism	Suitable Sample	Non-Suitable Sample	Notes
ZnSe	Good throughput	General organic substance	Hard powder, acidalkaline, high RI sample	In case of hard powder or hubbly sample, diamond is recommended
Diamond	Intensity, durability, measurement	Hard powder, General organic substance	High RI sample	Poor S/N ratio in the region around 2000 cm-1, due to internal absorption
Ge	Analysis for high RI sample	Sample including carbon	Hard powder, acidalkaline	Weak absorption due to small depth of penetration

*3 Case of measurement using ATR PRO 450-S, standard FTIR.
*4 If the measurement is needed in the wavenumber range below 400 cm-1, please contact local JASCO distributor.

Experimental

Suitable measurement example using ZnSe and Ge prism. Sample: ethanol — **Figure 1.** Suitable measurement example using ZnSe and Ge prism.
Sample: ethanol

Keywords

280-AT-0003, ATR, prism, diamond, Ge, ZnSe, refractive index

This document has been prepared based on information available at the time of publication and is subject to revision without notice. Although the contents are checked with the utmost care, we do not guarantee their accuracy or completeness. JASCO Corporation assumes no responsibility or liability for any loss or damage incurred as a result of the use of any information contained in this document. Copyright and other intellectual property rights in this document remain the property of JASCO Corporation. Please do not attempt to copy, modify, redistribute, or sell etc. in whole or in part without prior written permission.

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ATR PRO ONE
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About the Author

Dr. Carlos Morillo received his Post Doc at Advanced Industrial Science & Technology in Fukuoka and was a Research Scientist at Kyushu University in Japan where he lived for several years. Carlos received his Doctor of Engineering from Kyushu University and his Masters and BS from Simon Bolivar University in Caracas Venezuela. He is an Applications Scientist at JASCO.