VariGATR™ Grazing Angle Accessory

The VariGATR™ grazing angle ATR accessory is a revolutionary approach to the analysis of monolayers on semiconductor and metallic substrates. The VariGATR™ is variable angle, so the incident angle can be optimized for the highest sensitivity with these types of samples. Its specially designed pressure applicator is optimized for delivering good contact between the sample and the Ge ATR crystal. The VariGATR™ is excellent for rapid, repeatable measurements and provides at least an order of magnitude increase in sensitivity relative to grazing angle methods. In addition, it offers the convenience of an easy to use, fully prealigned, horizontal sampling accessory.

Variable grazing angle ATR accessory
Model No.
NOTE: A Model No. ending in "XXX" denotes spectrometer code.

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  • Convenient horizontal sampling surface.
  • Built-in pressure applicator with slip-clutch for reproducible pressure application.
  • Continuously variable angle from 60º to 65º allowing optimization for maximum sensitivity.
  • Anti-backlash mechanism allows for accurate, reproducible angle selection.
  • Mounted Ge ATR crystal.
  • Accommodates samples up to 8" in diameter with center-sampling of discs up to 6" in diameter.
  • PermaPurge™ for rapid purging of the system.
  • Options include:
    • Wire Grid Polarizer for enhanced spectral contrast and orientation studies. Includes slide plate mount.
    • Force sensor with digital read-out for precise measurement of the force applied to achieve contact between the ATR crystal and the sample.
    • Low-torque slip-clutch available.
    • Angular scale viewing aide for large samples.
  • Ge hemispherical ATR crystal.
  • Built-in pressure applicator, designed to accommodate large samples.
  • Mounting hardware for the specified spectrometer.
Model No. Product Description Price
GAT-V-VMR Angular Scale Viewer for VariGATR Use with large samples N/A
GAT-V1-FSD Force Sensor for the VariGATR, 110V N/A
GAT-V2-FSD Force Sensor for the VariGATR, 220/240V VariGATR digital force read-out N/A
PWC-GATR-XXX VariGATR mount for PWD polarizer Polarizer holder only N/A
PWD-GATR-XXX Wire Grid Polarizer, VariGATR VariGATR Polarizer (KRS-5 Substrate), includes mount N/A
SLP-CLL 24 in-oz. Slip-Clutch for MVP-Pro and VariGATR Delivers limited reproducible force for ATR N/A
Model No. Product Price
GATR-PAD Pressure Pads (5) for VariGATR, GATR and AccessATR $34.00
Model No. Product Price
GATR-ATR-J1 Ge Mounted Hemisphere for VariGATR $2,508.00
Model No. Product Description Price
CCS-004 CristalCalc Software ATR calculator $191.00
IRS-671 Internal Reflection Spectroscopy by N.J. Harrick $0.00
IRS-RS1 Internal Reflection Spectroscopy: Review and Supplement by Francis M. Mirabella, Jr. and N. J. Harrick $0.00

The VariGATR is a single reflection ATR accessory designed for analyzing monolayers and adsorbed species on semiconductor and metallic substrates.

The VariGATR integrates the theoretical conditions that provide the highest sensitivity to these extremely thin films¹ ² ³ in a convenient horizontal ATR sampler. The VariGATR™ features a Ge ATR crystal for use from 5000 to 650 cm-1. Its incident angle can be varied from 60º to 65º, making it possible to optimize the angle for any given spectrometer and sample. Its specially integrated Slip-Clutch pressure applicator optimizes contact between the sample and the relatively small active portion of the crystal. For greater sensitivity, a polarizer can be added to the VariGATR™ and, for more precise measurements of the force applied to the sample by the pressure applicator, a force sensor with digital read-out is available.

Figure 1. ATR Spectrum of an Organic Monolayer on Silicon, Measured at a 65º Incident Angle

Figure 2. ATR Spectrum of an Organic Monolayer on Gold, Measured at a 65º Incident Angle.

Figure 3. ATR Spectrum of a Thin Film on Si, Measured at Incident Angles of 60º (red) and 65º (blue).

Figures 1 and 2 demonstrate the high sensitivity of the VariGATR™ to monolayers. Figure 1 is a spectrum of an organic monolayer on a polished silicon surface. Figure 2 shows the spectrum of a monolayer on a gold-coated glass substrate. Figure 3 shows spectra of a thin film on Si for two different angles. For this particular film, the lower angle was closer to the experimental critical angle and hence provided stronger band intensities.

For sampling versatility, the VariGATR™ can also be used to analyze liquids, powders, pastes, and other solids. It is especially useful for samples with intense spectral bands. Such samples might otherwise exhibit too high absorbance or band distortions.

¹ M. Milosevic and S. L. Berets, 'ATR of Monolayers on Si and Neat Powders by Single Reflection ATR,' PittCon 2002 invited paper.

² M. Milosevic, S. L. Berets, and Y. Fadeev, 'Single Reflection Attenuated Total Reflection of Organic Monolayers on Silicon', Appl. Spectros., 57 (6), 4724 (2003).

³ Milan Milosevic, Violet Milosevic, and S. L. Berets, 'Grazing Angle Attenuated Total Reflection Spectroscopy: Fields at the Interface and Source of the Enhancement', Appl. Spectros, 61(5), 530 (2007).