Based on Michelson Interferometer

The MIR8035 uses a scanning Michelson Interferometer design. Optical layout includes corner cubes and a retro-reflector, which makes this unique layout immune to tilt and shift. The retro-reflector and beam splitter are mounted together, providing accurate alignment while desensitizing the system to vibrations and temperature variations. This "unibody" approach to the beam splitter makes for easy interchangeability with a minimum of realignment required. The beam splitter is made of a special material that transmits half of the radiation striking it and reflects the other half. Radiation from the source strikes the beam splitter and separates into two beams. One beam is transmitted through the beam splitter to the fixed mirror and the second is reflected off the beam splitter to the moving mirror. The fixed and moving mirrors reflect the radiation back to the beamsplitter. Again, half of this reflected radiation is transmitted and half is reflected at the beam splitter, resulting in one beam passing to the detector and the second back to the source.

Wide Spectral Coverage with High Resolution

The MIR8035 series FT-IR scanner is capable of high resolution because the resolution limit is simply an inverse of the achievable optical path difference, OPD. Therefore, a 2 cm OPD capable instrument can reach 0.5 cm-1 resolution.

Compatible with a Wide Range of Detectors, Sources, and Accessories

Oriel Instruments utilized a modular approach when designing the FT-IR Spectrometer Solution. We made the components that restrict the use of FT-IR instruments (sources, detectors, and sample compartments) interchangeable, so users don’t have to break it down completely when a change is required – simply switch out the component(s). A complete FT-IR Spectrometer Solution includes: a light source , the MIR8035 scanner with a beam splitter and window, a detection system, and the MIRLab software installed on laptop computer.

Includes Laptop Pre-installed with MIRLab Software

We didn't limit the flexibility of the Oriel Instruments' MIR8035 FT-IR scanner to its hardware. We include MIRLab™ software, which is a LabVIEW™ based, USB- compatible application integrating the MIR8035 scanner with computer control. It is compatible with Windows 10, 32- and 64-bit. It enables users to set up experiments, control the instrument, acquire spectra, and generate reports. The MIR8035 scanner ships with a high quality laptop computer with the software pre-installed.

Graphic presentation of the MIRLab software

Typical FT-IR Experiment

FT-IR experiments are easy with the MIR8035. Very simply, the scanner modulates the radiation from the source or sample, and the electronics board (in the scanner) digitizes the analog signals from the detection system and sends them to a computer through a USB 2.0 interface. MIRLab software is used for instrument control and data handling.

Schematic of a standard FT-IR setup

FT-IR Spectroscopy

Infrared spectroscopy (IR spectroscopy) is the subset of spectroscopy that deals with the infrared region of the electromagnetic spectrum. It covers a range of techniques, the most common being the "mid infrared" (MIR) region and the absorption spectroscopy. Infrared spectroscopy exploits the fact that molecules have specific frequencies at which they absorb the excitation energy and rotate or vibrate corresponding to discrete energy levels. The mid-infrared, approximately 6,000-700 cm-1 (1.7–14 µm), is typically used to study the fundamental vibrations and associated rotational-vibration molecular structures and is the most widely used FT-IR region for a wide variety of industrial applications. When infrared light is passed through an organic compound, some of the frequencies are absorbed, while other frequencies are transmitted through the sample without being absorbed. Plotting absorbance or transmittance against frequency or wave number will result in an infrared spectrum. All the peaks of the spectrum are not of analytical importance. The characteristic peaks are of main interest. Comparison of the peaks to previously run materials in a library can provide positive identification. The goal of any absorption spectroscopy (FTIR, UV-Vis spectroscopy, etc.) is to measure how well a sample absorbs light at each wavelength. Fourier Transform Spectroscopy shines a beam containing many frequencies of light at once, and measures how much of that beam is absorbed by the sample. Next, the beam is modified to contain a different combination of frequencies, giving a second data point. This process is repeated many times. Afterwards, a computer takes all this data and works backward to infer what the absorption is at each wavelength. The beam described above is generated by starting with a broadband light source—one containing the full spectrum of wavelengths to be measured. The light shines into a Michelson interferometer — a certain configuration of mirrors, one of which is moved by a motor. As this mirror moves, each wavelength of light in the beam is periodically blocked and transmitted by the interferometer, due to wave interference. Different wavelengths are modulated at different rates, so that at each moment, the beam coming out of the interferometer has a different spectrum. A computer is used to turn the raw data (light absorption for each mirror position) into the desired result (light absorption for each wavelength). The processing required turns out to be a common algorithm called the Fourier transform (hence the name, Fourier Transform Spectroscopy). The raw data is an interferogram.

Typical FTIR Applications

Thanks to a decade of continuous technical development of FT-IR spectroscopy (increasing throughput, dynamic alignment, more sensitive detectors, brighter sources, increasing scanning speed, development of focal plane array detectors, flexible spectral manipulations and data handling, etc.), this method has developed a great number of new and unique applications. For example, the in situ IR absorption measurements, such as remote sensing using the sun, the sky, or natural hot objects as IR sources of radiation. These include a number of originally hot gaseous samples such as volcanic plumes, automobile gases, stack gas plumes, or flames related to environmental analysis of the atmosphere. There is a wide range of atmospheric environmental applications of FTIR spectroscopy; such as power plants, petrochemical and natural gas plants, waste disposals, agricultural sites, and industrial sites; as well as the detection of gases produced in flames, in biomass burning, and in flares.