A-How+Does+Infrared+Spectroscopy+Aid+in+Criminal+Investigations

**__By: David Wang __** Infrared spectroscopy is a type of absorption spectroscopy that uses the infrared portion of the electromagnetic spectrum to examine the composition of different samples. In order to understand infrared spectroscopy, we must first understand the function of a simple harmonic oscillator.  // When a metal ball is attached to a stationary frame through a spring, the sphere will oscillate once set in motion. The vibrate frequency is considered to be dependent on the mass of the sphere and the strength of the spring. With any of these 2 factors altered, the frequency will change and the vibration will be different. // We may consider the chemical bonds between the molecules as simple harmonic oscillators. The atoms of a particular molecule vibrate at different frequencies depending on their atomic mass, strength of the bond and energy levels. Smaller atoms and stronger bonds cause faster vibrations. Each compound contains a unique set of bonds and elements thus cause a unique set of vibrating frequencies. When the vibrating molecules are exposed to the infrared radiation, they will absorb the matching frequencies in the light. This absorption will provide more energy for the molecule to vibrate at a larger magnitude and lower the initial energy level of the IR radiation. The remaining light will pass through the sample molecule into a detector where the amount of energy absorbed at each wavelength is recorded. This can be done by scanning through the spectrum by a monochromatic beam or by using a Fronrier transform instrument to measure all wavelengths.
 * __How does Infrared Spectroscopy aid in Criminal Investigation. __**

Criminal Investigation Using infrared spectroscopy in criminal investigation is not a complicated process. Any samples of evidences collected at the crime scene can be used under IR radiation. For example, if a segment of car paint was collected by the investigators. They can use IR spectroscopy procedure to determine the composition of the paint and determine what vehicle processes that particular type of paint. If a bullet shell was collected at the crime scene, the IR spectroscopy can be used to determine the composition of the metal. From the metal composition, the investigators can be informed about what weapon took the shot and even which company manufactured the shell.

**__Sources __** John Black, BJ. (2009, June 14). //Infrared spectroscopy//. Retrieved from http://www.accessscience.com/abstract.aspx?id=344700&referURL=http%3a%2f%2fwww.accessscience.com%2fcontent.aspx%3fsearchStr%3dinfrared%2bspectroscopy%26id%3d344700 kelly silversmith, KD. (2003, February 6). //Infrared spectroscopy//. Retrieved from http://www.umsl.edu/~orglab/documents/IR/IR2.html Gregory Brust, IGB. (2010, March 30). //Infrared spectroscopy//. Retrieved from http://www.pslc.ws/macrog/ir.htm