IR spectroscopy introduction

1. IR SPECTROSCOPY
Presented by
Arunkumar rengaraj
Seo-Young Oh
Nano-Bio Analysis lab
Inha university

2. IR RADIATION
• Infrared radiation is popularly known as heat radiation.
• Infrared light from the Sun accounts for 49% of the heating of Earth
• It is electromagnetic radiation with longer wavelengths than those of visible light.

3. Infrared spectroscopy
Molecules absorb specific frequencies that are characteristic of their structure.
Absorbed radiation matches the transition energy of the bond or group that vibrates.
Transition energy calculated by
• Shape of the molecular (potential energy surfaces)
• Masses of the atoms
• Vibronic coupling
causing a change in the amplitude of molecular vibration

4. Energy Levels: Basic Ideas
About 15 micron radiationBasic Global Warming: The C02 dance …

6. Scanning monochromator method
where one wavelength at a time passes through the sample

7. Fourier transform infrared (FTIR) spectroscopy
It is a measurement technique that allows one to record infrared spectra.
Infrared light is guided through an interferometer and then through the sample (or vice versa).
Interferometry makes use of the principle of superposition
A moving mirror inside the apparatus alters the distribution of infrared light that passes through the interferometer. The signal
directly recorded, called an "interferogram", represents light output as a function of mirror position.

8. A data-processing technique called Fourier transform turns this raw data into the desired result (the sample's
spectrum.
Fourier transform
It is a mathematical transformation employed to transform signals between time (or spatial) domain
and frequency domain.
Fourier transform can be simplified to the calculation of a discrete set of complex amplitudes
FTIR improving both speed and signal-to-noise ratio.
A dispersive measurement requires detecting much lower light levels than an FTIR measurement.[3]

9. 1-Hexene
CH2
CH CH2
CH2
CH2
CH3
sp2
C-H
sp3
C-H stretch
C=C
stretch
out of plane
bendings (oops)

10. Toluene
CH3
sp2
C-H
sp3
C-H aromatic
C=C
aromatic oops

11. Cyclohexanol
OH
O-H
stretch
bending
C-O
stretch
sp3 C-H stretch