Attenuated total reflectance

Attenuated total reflectance

Attenuated total reflectance (ATR) is a sampling technique used in conjunction with infrared spectroscopy which enables samples to be examined directly in the solid or liquid state without further preparation.cite web | year=2005 | title=FT-IR Spectroscopy—Attenuated Total Reflectance (ATR) | work=Perkin Elmer Life and Analytical Sciences | url= | accessdate=2007-01-26]

ATR uses a property of total internal reflection called the evanescent wave. A beam of infrared light is passed through the ATR crystal in such a way that it reflects at least once off the internal surface in contact with the sample. This reflection forms the evanescent wave which extends into the sample, typically by a few micrometres. The beam is then collected by a detector as it exits the crystal.

This evanescent effect works best if the crystal is made of an optical material with a higher refractive index than the sample being studied. In the case of a liquid sample, pouring a shallow amount over the surface of the crystal is sufficient. In the case of a solid sample, it is pressed into direct contact with the crystal. Because the evanescent wave into the solid sample is improved with a more intimate contact, solid samples are usually firmly clamped against the ATR crystal, so that trapped air is not the medium through which the evanescent wave travels, as that would distort the results.

Typical materials for ATR crystals include germanium, KRS-5 and zinc selenide, while silicon is ideal for use in the Far-IR region of the electromagnetic spectrum. The excellent mechanical properties of diamond make it an ideal material for ATR, particularly when studying very hard solids, but its much higher cost means it is less widely used.


*cite book |title= Internal Reflection Spectroscopy|last= Harrick |first= N.J. |authorlink= |year= 1967 |publisher= John Wiley & Sons Inc|isbn= 978-0470352502 |pages= 342


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • attenuated total reflection — (ATR)    Reflection that occurs when an absorbing coupling mechanism acts in the process of total internal reflection to make the reflectance less than unity …   Forensic science glossary

  • Total internal reflection — The larger the angle to the normal, the smaller is the fraction of light transmitted, until the angle when total internal reflection (blue line) occurs. (The color of the rays is to help distinguish the rays, and is not meant to indicate any… …   Wikipedia

  • ATR — Attenuated Total Reflectance (Academic & Science » Physics) Attenuated Total Reflectance (Academic & Science » Electronics) Automatic Target Recognition (Governmental » Military) **** Atrophy (Medical » Physiology) *** Average True Range… …   Abbreviations dictionary

  • Perchlorate — Structure et dimensions de l ion perchlorate Modèle 3D de …   Wikipédia en Français

  • Perchlorate de francium — Perchlorate Structure et dimensions de l ion perchlorate …   Wikipédia en Français

  • ATR-Spektroskopie — (von engl. attenuated total reflection, dt. abgeschwächte Totalreflexion) ist eine infrarot spektroskopische Methode für die Oberflächenuntersuchung von undurchsichtigen Stoffen wie z. B. Lackschichten oder Polymerfolien und auch flüssigen Proben …   Deutsch Wikipedia

  • List of materials analysis methods — List of materials analysis methods: Contents: Top · 0–9 · A B C D E F G H I J K L M N O P Q R S T U V W X Y Z μSR see Muon spin spectroscopy …   Wikipedia

  • ATR-Infrarotspektroskopie — (von englisch attenuated total reflection, dt. abgeschwächte Totalreflexion) ist eine Probentechnik der Infrarotspektroskopie (IR Spektroskopie) für die Oberflächenuntersuchung von undurchsichtigen Stoffen wie z. B. Lackschichten oder… …   Deutsch Wikipedia

  • Chemical imaging — (as quantitative chemical mapping) is the analytical capability to create a visual image of components distribution from simultaneous measurement of spectra and spatial, time informations.[1][2] The main idea for chemical imaging, the analyst may …   Wikipedia

  • Evanescent wave — Schematic representation of evanescent waves propagating along a metal dielectric interface. The charge density oscillations, when associated with electromagnetic fields, are called surface plasmon polariton waves. The exponential dependence of… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.