Major types of spectroscopy

Scattering and other forms of spectroscopy Rely on the fact that electromagnetic radiation has other interactions with matter beyond that of simple absorption and emission. These interactions generate other measurable quantities such as scattering of polarized light (e.g. circular dichroism), and changes of spectral features of chemical bonds (e.g. Raman spectroscopy). 

As mentioned above, spectroscopy is an umbrella term for a range of techniques that allow identification, quantification and determination of molecular stmcture of biomolecules. This technology also allows the bioanalytical chemist to follow key reaction pathways including, for example, the rate of an enzyme-catalysed reaction. 

Background and principles UV spectroscopic analysis was one of the first applications of spectroscopy in an analytical context. While a powerful technique of yesteryear, this method is now rather restricted in its use in a modem bioanalytical laboratory. However, UV/visible spectroscopy is still used in specific biochemical analyses, such as dyestuffs in forensic applications. Despite these limitations, a bench spectrophotometer that measures UV/visible absorbance is commonly found in both teaching and research laboratories. In order to better understand the underlying principles it is necessary to consider the excitation of electrons, electronic transition and how this is related to energy and absorbance. 

Fundamentals of spectrophotometer readings In order to best understand the use of UV/visible spectrophotometry and a spectrophotometer instrument it is important to first understand the data that can be derived from the use of this technique/equipment. The fundamental outcome from the use of a spectrophotometer is a measure of transmittance or absorbance. As the names suggest, transmittance (T) is the amount of light that is transmitted through the sample solution whereas absorbance (A) is a measure of light absorbed by the sample solution. Modern instmments can provide readings of both transmittance and absorbance (or its reciprocal 1/A) normally the primary reading for most bio-analytical applications is absorbance. However, it is important to appreciate that transmittance and absorbance are related by fundamental equations. 

For the majority of bioanalytical applications, measures of absorbance will be made at defined wavelengths, and the absorbance reading is sometimes referred to as the optical density (OD) reading. The absorbance is calculated from the transmittance measure using the logarithmic relationship described by the following equation  

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Photophysics involves the absorption, transfer, movement, and emission of electromagnetic, light, energy without chemical reactions. By comparison, photochemistry involves the interaction of electromagnetic energy that results in chemical reactions. Let us briefly review the two major types of spectroscopy with respect to light. In absorption studies, the detector is placed... 

To distinguish between various major types of spectroscopy. 

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