Polarization Modulation Infrared Reflection Absorption Spectrometer PM-IRRAS


The PM-IRRAS is an infrared spectrometer specifically for IR analysis of monolayers floating on an aqueous subphase or deposited on reflective substrates. It is highly sensitive and very surface specific enabling measurements in ambient conditions. The innovative goniometric configuration allows easy angle adjustment and fast setup time.

FTIR reflection spectroscopy
Polarisation modulation
Monolayer sensitivity
Infrared absorption of the PM-IRRAS is in the range of 800 - 4000 cm-1

The PM-IRRAS technology allows the measuring of surface specific FT-IR spectra of materials because of the differences in the reflection of p- and s-polarized light from interfaces. The polarization modulation method almost completely eliminates background signals coming from environmental factors such as water vapor and CO2 which removes the need for protective gasses as with other IR reflection instruments. By positioning the spectrometer and detector on a goniometer above the surface the experimental setup is greatly simplified and provides you with results within minutes instead of days. This open design also allows combined use of other complementary equipment like external UV light source and temperature heater. The instrument can be positioned above a fully equipped analytical Langmuir Trough, facilitating accurate monolayer studies without restrictions.

Chemical composition of thin films

PM-IRRAS is a highly surface specific FT-IR method that is capable of detecting chemical compositions from interfacial films down to one molecule thick films. The PM-IRRAS technique allows enhanced detection on substrates and measurements from the air-water interface. Changes in the PM-IRRAS signal intensity and position can be used to infer molecular absorption/desorption behavior and kinetics, molecular packing, phase transitions, hydration, hydrogen bonding and different surface reactions in a thin film. Additionally in PM-IRRAS the properties of the polarized light can be used to determine the molecular orientation in a film.

The reported infrared absorption of the PM-IRRAS is in the range of 800 - 4000 cm-1 making it possible to detect:

Chemical composition of thin films

Chemical composition can be detected from thin films that are just one molecule thick

Adsorption / desorption and surface reactions in mono- and multilayers

Studying interaction of biomolecules using cell membrane models can provide means to understand reactions related to drug delivery and the membrane behavior itself. These kinds of model systems are employed in several application areas, such as drug development, food technology, and biological and biochemical research.

Phase transitions in thin films

Monolayer phase transitions can be detected with PM-IRRAS. A typical example would be protein denaturation at the interface or deposited layer.

Hydrogen bonding
Molecular orientation


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Product Manager - Ellipsometry & Surface Science
+49 6151 8806-68
Fax: +49 6151 8806968

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