VATR Description:

The Variable Angle ATR, is a traditional in-compartment accessory with the ATR crystal mounted vertically with respect to the spectrometer baseplate. Its optical layout allows continuous adjustment of the incident beam angle between 30 to 60 degrees. This accessory is suitable for the analysis of solids, films and coatings, but for obvious reasons, it cannot be used for working with liquids.  VATR is an excellent, low-cost tool for teaching the principles of internal reflection spectroscopy, and for basic research.

30° to 60° variable angle of incidence

Economical introduction to ATR techniques

Full control over number of reflections and depth of penetration

Variable Angle ATR: A Primer

Variable Angle Attenuated Total Reflectance (VA-ATR) is a specialized technique within ATR spectroscopy that allows researchers to vary the angle at which the incident infrared (IR) beam strikes the ATR crystal or prism. By adjusting the incident angle, scientists can control the depth of penetration into the sample and obtain information from different depths within the sample.

Key features and considerations of Variable Angle Attenuated Total Reflectance (VA-ATR) include:

1. Depth Profiling: One of the main advantages of VA-ATR is its capability to perform depth profiling analysis. By changing the incident angle of the IR beam, researchers can probe different layers within the sample, providing valuable information about the sample's composition as a function of depth.

2. Penetration Depth Control: The depth of penetration into the sample is inversely related to the incident angle. Lower angles provide deeper penetration, while higher angles yield shallower penetration. This control over penetration depth enables researchers to investigate surface layers and buried interfaces within the sample.

3. Sampling of Heterogeneous Samples: VA-ATR is particularly useful for heterogeneous samples, where different layers or components are present. Researchers can selectively probe each layer by adjusting the incident angle accordingly.

4. Depth Resolution: The depth resolution of VA-ATR depends on several factors, including the refractive indices of the sample and the ATR crystal, as well as the angle range used. Finer angle increments typically result in improved depth resolution.

5. Sample Type: VA-ATR can be applied to a wide range of sample types, including liquids, solids, gels, and films. It is especially useful for samples with non-uniform composition or layered structures.

6. Optical Setup: The VA-ATR experimental setup may involve motorized stages or manual adjustments to vary the angle of the incident beam. In some cases, dedicated VA-ATR accessories or attachments are available for compatible spectrometers.

7. Data Analysis: Analyzing VA-ATR data requires careful consideration of the angle-dependent information obtained. Proper data processing and modeling may be needed to interpret depth profile data accurately.

VA-ATR is a valuable tool in various fields of research, including materials science, chemistry, and biomedical studies. It enables researchers to gain insights into the composition and properties of layered or heterogeneous samples, as well as surface interactions and adsorption phenomena.

It is important to note that VA-ATR measurements can be more time-consuming than traditional ATR measurements due to the need to acquire data at multiple angles and analyze the depth profile data properly. However, the depth-resolved information obtained makes VA-ATR a powerful and informative spectroscopic technique for many applications.