Effective absorption coefficient and effective thickness in attenuated total reflection spectroscopy
| Autor: | Hans Arwin, Arturo Mendoza-Galván, J G Méndez-Lara, Kenneth Järrendahl, Reina Araceli Mauricio-Sánchez |
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| Rok vydání: | 2021 |
| Předmět: |
Total internal reflection
Materials science Absorption spectroscopy business.industry Atom and Molecular Physics and Optics 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics Atomic and Molecular Physics and Optics 010309 optics Wavelength Optics Attenuation coefficient Attenuated total reflection 0103 physical sciences Atom- och molekylfysik och optik 0210 nano-technology business Penetration depth Absorption (electromagnetic radiation) Spectroscopy |
| Zdroj: | Optics Letters. 46:872 |
| ISSN: | 1539-4794 0146-9592 |
| DOI: | 10.1364/ol.418277 |
| Popis: | Since the introduction of attenuated total reflection (ATR) spectroscopy for the characterization of materials, attempts have been made to relate the measured reflectivity ( R ) to the absorption coefficient ( α ) of the absorbing material of interest. The common approach is limited to the low absorption case under the assumption R ∼ exp ( − α d e ) , where d e is an effective thickness, which is evaluated for the lossless case. In this Letter, a more detailed derivation leads to R = exp ( − β d p / 2 ) , enabling the definition of an ATR-effective absorption coefficient β and the penetration depth d p of the electric field in the absorbing material. It is found that β ∼ 4 π ε 2 / λ , where ε 2 is the imaginary part of the complex dielectric function of the absorbing material, and λ is the wavelength. An alternative formulation is R = exp ( − α d ef ) , where d ef is a generalized effective thickness for arbitrary strength of absorption which reduces to d e in the low absorption limit. The experimental data for water, the biopolymer chitosan, and soda-lime glass prove the reliability of the ATR-effective absorption coefficient in the infrared range. |
| Databáze: | OpenAIRE |
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