Various Spectroscopic Techniques
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5 Various Spectroscopic Techniques RAMESH K SHARMA1*
ABSTRACT
Our eye is a finest detector in the nature which can identify different colors at very high resolution. The detection band width of eye is only restricted to visible region which is a very small fraction of electromagnetic wave spectrum consisting of a range from gamma rays to radio waves. To study the interaction of these waves with matter several specialized instruments in different ranges of electromagnetic spectrum are developed which are called spectroscopes. Different regions of spectrum have different instruments associated with them. The change in electronic states is associated with Xrays, UV and Visible region, change in vibration and rotational states can be studied with Infrared measurements and similarly nuclear spins can be studied in radio wave region. In this chapter the spectroscopic techniques such as UV-Visible, IR spectroscopy, X-ray diffraction, X-ray fluorescence and NMR are focused. Basic instrumentation and the typical output are discussed. Although there are other methods such as Electron Beam Spectroscopy and Mass Spectroscopy which are very powerful techniques but in this chapter the focus is on the techniques used in electromagnetic spectrum only. Key words: Spectroscopy, Ultraviolet, Visible, Infrared, X-ray, Nuclear magnetic resonance. SPECTROSCOPY
Spectroscopy is the observation of interaction of electromagnetic waves with matter. This term originated for the study of visible light dispersed 1
Sophisticated Analytical Instrumentation Facility (SAIF), Panjab University, Chandigarh, India. *Corresponding author: E-mail:
[email protected]
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Environmental Pollution: Monitoring, Modeling and Control
by a prism as per the wavelengths of different colors present in the visible region. Since it is study of electromagnetic radiation so one must be conversant with the nature of these radiations.
About Electromagnetic Radiation EM radiation is a form of energy having dual nature i.e., to explain some phenomenon such as interference it can be considered as waves whereas in some cases it can be considered as particle. So, the exact nature of EM radiation cannot be defined but dual nature explains all the phenomena.
Wave Nature of Electromagnetic Radiation Electromagnetic radiation comprises of alternating electric and magnetic field moving perpendicular to each other and it propagate through space in a straight line with a constant velocity in the vacuum. The velocity in vacuum is 299,792,458 m/s and is known as constant represented by c. When EM radiation enters in the medium other than the vacuum the velocity decreases and is represented by v. The difference between c and v is very small (
