The computational power of the FTIR spectrometer makes it possible

The Michelson interferometer is the foundation for two different sensor technologies known as ftir spectrometers (Fourier Transform Infrared) and FTS (Fourier Transform Spectroscopy). In its original form, the Michelson interferometer was made up of two flat mirrors that were positioned at 90 degrees to each other, and a beam splitter that was mounted on the line that divided the two mirrors at 45 degrees.

In most cases, one of the mirrors is held in place, and the other mirror is mounted in a way that allows it to be translated while still preserving its precise alignment in relation to the mirror that is held in place.

The incoming optical radiation is modulated by the Michelson interferometer in a continuous and smooth manner by changing the optical path difference (OPD) between the two possible paths in the interferometer. Some FTIR sensors do use a step scan approach. The interferometer is constructed using two mirrors that are angled at a right angle to one another and are separated from one another by a beam splitter and a beam compensator pair.

It is possible to alter the path difference, which is referred to as retardation, by moving one of the two mirrors at a constant speed over a predetermined distance. When the mirror has completed its journey across the required distance, which is determined by the required spectral resolution, it is rapidly brought back to its starting position so that the subsequent scan can begin.

During the time that the moving mirror is in motion, each wavelength of the radiation that was collected is modulated at a distinct frequency. This frequency is a function of both the wavelength of the radiation and the speed at which the moving mirror is moving.

As an illustration, if a laser with a wavelength of 10 micrometers CO2 was used as the source of radiation, and the interferometer mirror was moving at a speed of 10 centimeters per second (optical), then the signal that was generated would be a sine wave with a constant amplitude and a constant frequency ( 1/10 m multiplied by 10 centimeters per second equals 10 kilohertz). An interferogram is produced by assuming a broadband source such as a blackbody, taking into account all of the wavelengths that comprise the target radiation, and then adding all of these sinusoids together. This results in the production of an interferogram.

Because of this, the interferogram can be thought of as a coded representation of the target spectrum. The spectrum of the target radiation can be obtained through the Fourier Transform or through the decoding of the interferogram. Because of their primary application in the infrared region of the electromagnetic spectrum, which is where the detectors can most benefit from their superior sensitivity, these spectrometers are also known as Fourier transform infrared spectrometers.

Why Use FTIR

Why bother dealing with the additional complexity that is caused by encoding the data if you are going to have to use the Fourier Transform to decode it? When compared to grating, prism, and circular variable filter (CVF) spectrometers, Michelson interferometers offer a significant advantage in terms of their sensitivity.

There are two main factors that contribute significantly to the advantage of sensitivity. The first is something that could be called a multiplex advantage. The single detector of the Michelson interferometer views all of the wavelengths simultaneously (within the passband of the sensor) throughout the entirety of the measurement. Because of this, the detector is effectively able to linger on each wavelength for the entirety of the measurement time, which enables it to measure more photons. The multiplex advantage refers to this improvement, which, in practice, lengthens the amount of time required for integration.

The second advantage is that it has the capability of gathering more light, which results in a larger throughput. In contrast to dispersive or CVF instruments, the interferometer does not have aperture (slit width or height) restrictions of the same severity. This translates into a significantly increased capacity for throughput as well as light gathering. In comparison to other spectrometers, the Michelson ftir spectrometers is able to provide a higher level of sensitivity within the infrared region of the spectrum as a result of both of these advantages.

If there was ever anyone who had any doubt that FTIR analysis is a lifetime study, that person hasn't been to a research library in the life sciences or chemistry in quite some time. Since the advent of the Internet, a significant amount of information that was formerly only accessible in the form of printed books is now also available in an online and digital format. The following is a rundown of some of the resource materials that we consider to be some of the best available for learning more about spectroscopy in general and FTIR in particular.

We do not judge a book by its cover, and we do not judge a website based on the number of bells and whistles that it has or does not have. Because we are aware that researchers and technicians are extremely busy doing what they do best—being researchers and technicians—we do not place excessive demands on them in terms of website design. This straightforward website consists of only one page and offers links to recommended books that can be purchased from Amazon. com. The topics that are discussed in these books range from the most recent developments in infrared group frequencies to the most fundamental aspects of molecular spectroscopy. The inclusion of a number of web links to online magazines, articles, and tables is an additional perk that can be enjoyed.