Frequently Asked Questions

General Questions

What is transmission spectroscopy?

Light from a source passes through a sample to be registered by a detector. The method of analysis is based upon the absorption of the infrared beam by a sample at specific wavelengths or frequencies of light.

A sample presented to the infrared beam in this configuration will produce an infrared spectrum unique to the sample itself. In this way, infrared spectroscopy is used as a qualitative measurement of a sample.

What is reflectance spectroscopy?

Reflectance measurements can be divided into two basic categories – internal or external reflectance. The technique of Attenuated Total Reflection (ATR) is employed for internal reflectance measurements as the beam of infrared radiation passes through an ATR element (crystal) in contact with the sample.

For external reflectance measurements, the infrared beam of radiation is reflected directly from the sample surface. This type of external reflectance measurement can also be divided into two types – Diffuse or Specular.

How easy is it to change a baseplate-mounted accessory?

Most Specac accessories are installed into a spectrometer sample compartment via an adapter baseplate. The most commonly used type is known as a Benchmark ™ baseplate. The accessory locates onto the top of the Benchmark ™ baseplate and is held secure by a single thumbscrew fixing, usually into a location pillar at the front of the baseplate.

The spectroscopic ranges explained

Particular regions of the Electromagnetic Spectrum are commonly assigned with terms such as Visible or Near IR (Infrared) etc. For reference purposes, frequency and wavelength ranges of these various spectral regions have been set by the Joint Committee on Nomenclature in Applied Spectroscopy.

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Transmission Spectroscopy

What mulling agents do Specac supply?

Specac supply two types of mulling agents, Nujol and Fluorolube, that are used with ground solid samples to be runs as liquid mulls.

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What pathlength gas cell do I need for my sample?

In order to determine the pathlength of a gas cell for the concentration of gas to be measured, the measured absorbence (A) is related to the concentration of gas (C) by the usual Beer’s Law relationship.

A = - Log10 (I/Io) = a.C.L 

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What samples can I analyze using a DC3?

The DC3 diamond compression cell P/N GS02555 enables samples to be compressed to an ideal thickness for transmission experiments.

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How do I set up gas line plumbing of a long pathlength gas cell?

This depends on how gas supplies are plumbed to be introduced into the internal gas cell cylinder area where the beam of light traverses between the internal mirrors for multiple passing to provide a long pathlength.

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How can I align a Cyclone Gas Cell?

For mirror alignment of any version of Cyclone gas cell, but most especially for the variable pathlength cell options, Specac thoroughly recommend use of the laser alignment accessory P/N GS24500.

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What are the advantages of the Advanced High Temperature High Pressure Cell

When ordering the High Temperature High Pressure Cell (HTHP Cell) as the advanced version P/N 05855, there are 3 window assemblies supplied...

What kind of measurements can I make with the High Temperature High Pressure Cell?

The High Temperature High Pressure Cell (HTHP Cell) P/N 5850 has the capability of being operated at temperatures approaching 800C and pressures up to 1000psi.

Reflectance Spectroscopy

What is Band Distortion and Band Shift in ATR?

When obtaining an Infra Red spectrum via ATR spectroscopy, the spectrum will be different to that obtained for the same sample when collected as a transmission spectrum.

How do I realign a Golden Gate ATR?

The ZnSe or KRS-5 lenses of a Golden Gate™ ATR Accessory focus the beam of a light signal to pass through the small aperture of the diamond crystal assembly.

How do I calibrate a Heated Golden Gate?

Within the top plate area of the Heated Golden Gate diamond ATR accessory, the temperature measuring thermocouple is situated as close as it can be to the diamond to record the actual surface temperature.

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How do I realign my Selector Diffuse Reflectance Accessory?

Throughput from a diffuse reflectance accessory is usually quite low in respect to an unobstructed beam.

How do I realign my Monolayer accessory?

From installation of the Specac monolayer grazing angle accessory into a spectrometer sample compartment, if there is no signal throughput registered when the reference reflectance mirror is in position on the sampling platform and the “butterfly arms” have both been set to the same incidence angle (nominally 45°), then it is possible either one or both of the adjustable mirrors at the end of the butterfly arms is/are not correctly aligned.

What are the pressure limits of a Diamond Golden Gate ATR?

For solid samples on a Golden Gate™, an external force from an applied load is needed to bring the sample into good contact with the diamond crystal.

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How do I choose an ATR accessory for my application?

Attenuated Total Reflectance (ATR) spectroscopy can be used for samples that are difficult to analyze by a transmission technique.

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What Gateway ATR accessories are available?

Gateway™ ATR is a six reflection horizontal ATR sampling system designed to fit into a wide range of FTIR spectrometers.

Do I need a Torque Wrench for the Golden Gate?

On the Golden Gate™ ATR accessory a solid sample is bought into contact with the ATR crystal by pressure on the sample via an anvil.

How do I remove the Torx Screw for the Golden Gate ATR?

For replacement of a Torx screw in the torque screw mechanism of a Golden Gate ATR accessory, it is necessary to establish if it is a Mark 1 or Mark 2 Golden Gate ATR. 

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Sample Preparation

Do Specac provide a Vacuum Pump?

The vacuum pump GS03640 is a dual voltage operation (220 volts and 110 volts), two stage vacuum pump capable of pulling a vacuum to 0.05 Torr or better. It is an ideal vacuum pump to use with the Specac Accessories that have the capability of being operated under these vacuum conditions.

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How can I troubleshoot my Manual Press?

If there is a problem with an Atlas Manual 15T or 25T hydraulic press, before Specac can advise anything to help, certain details must be known about the actual press itself and the nature of the problem to clarify what may be required to solve the problem.

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How do I clean my Evacuable Die?

The Atlas Evacuable Pellet Dies are made from a grade of stainless steel 440C. If subjected to mineral acids (such as HCl) for prolonged periods then it will be attacked.

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How do I prepare high quality KBr pellets?

Generally, it is easy to produce a good quality KBr pellet if an evacuable pellet die is used correctly. However, some faults in the produced sample pellet may occur due to a variety of reasons.

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How thick should my film be when using the Film Maker?

From experience with using the Atlas Film Maker Accessories, it is rare to produce an exact film thickness as stated by the thickness value on the spacer ring.

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What are the load limits for Evacuable Dies?

As the dies grow in size for their diameter, so their recommended load limit increases as there is a larger area associated with being compressed for the die pellet.

What is the difference between the Power and Autotouch presses?

The Atlas Power 8T, Power 15T and Power 25T presses offer a load range capability of 1 to 8 tons, 2 to 15 tons and 3 to 25 tons respectively. 

Which hydraulic press is best for my application?

Specac makes a variety of Atlas hydraulic presses for a wide range of pressing applications.