It is a PerkinElmer Spectrum One FT-IR spectrometer.
About the Instrument:
This instrument can operate in ratio, single-beam, or interferogram mode. It gives data collection over a total spectral range of 7800 to 370 cm-1. It includes a mid infrared detector – either DTGS (deuterated triglycine sulphate) or LiTiO3 (lithium tantalate) – as standard, and the option of using MCT (Mercury Cadmium Telluride) or PAS (a photo acoustic detector).
Theory of operation:
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 a form of absorption spectroscopy.
The infrared portion of the electromagnetic spectrum is divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum. The far-infrared, approximately 400-10 cm-1, lying adjacent to the microwave regionhas low energy and may be used for rotational spectroscopy. The mid-infrared approximately 4000-400 cm-1 may be used to study the fundamental vibrations and associated rotational-vibrational structure. The higher energy near-IR, approximately 14000-4000 cm-1 can excite overtone or harmonic vibrations. The names and classifications of these sub-regions are merely conventions. They are neither strict divisions nor based on exact molecular or electromagnetic properties.
Infrared spectroscopy exploits the fact that molecules have specific frequencies at which they rotate or vibrate corresponding to discrete energy levels. These resonant frequencies are determined by the shape of the molecular potential energy surfaces, the masses of the atoms and, by the associated vibronic coupling. In order for a vibrational mode in a molecule to be IR active, it must be associated with changes in the permanent dipole. In particular, in the Born-Oppenheimer and harmonic approximations, i.e. when the molecular Hamiltonian corresponding to the electronic ground state can be approximated by a harmonic oscillator in the neighborhood of the equilibrium molecular geometry, the resonant frequencies are determined by the normal modes corresponding to the molecular electronic ground state potential energy surface. Nevertheless, the resonant frequencies can be in a first approach related to the strength of the bond, and the mass of the atoms at either end of it. Thus, the frequency of the vibrations can be associated with a particular bond type.