Applications - RAMAN SPECTROSCOPY

WHAT IS RAMAN SPECTROSCOPY? Raman spectroscopy is an analytical technique based on detection of scattered light and used for a variety of applications involving solid, liquid, and gas samples. The technique involves looking at scattered light from an irradiated sample. A small portion of the scattered light exhibits a slight shift in wavelength due to molecular vibrations in the sample, and this wavelength shift is used to analyze the sample. HOW DOES IT WORK? The basic components for Raman spectroscopy typically include a laser light source, collection optics to gather the Raman-scattered light, and a detection system. For biomedical applications, it is generally recommended that you work with laser light in the near-infrared (e.g. 785 or 830nm) to minimize potential problems with tissue fluorescence and tissue damage. Raman spectroscopy involves shining a laser onto a sample and examining the interaction between this light and the chemical bonds in the sample. This interaction is known as the Raman effect. When the sample is irradiated, most of the incident light is scattered at the same wavelength. This "elastic" type of scattering is known as Rayleigh scattering. However, a small fraction of the laser light will excite molecular vibrations in the sample and will be inelastically scattered, or scattered at a slightly different wavelength. This shift in the wavelength can be detected and used to make determinations about the sample. WHAT ARE ITS ADVANTAGES?  •• no special sample preparation required •• relatively quick process •• compatible with aqueous solutions (unlike IR spectroscopy, which results in a large proportion of the vibrational spectrum being masked by intense water signals) WHAT'S RAMAN SPECTROSCOPY USED FOR? •• provides details on the chemical composition, molecular structure, and molecular interactions in cells and tissues •• used to identify materials by characterizing the distinctive energies of the chemical bonds •• used to distinguish between different phases of the same material •• can provide information on strain and periodicity in modulated structures WHAT IS HOLOGRAPHY? Holography is the creation of a light wave interference pattern recorded on film or other suitable surface that can produce a 3D image when illuminated. HOW DOES IT WORK? Holography involves splitting a laser beam into two beams. The reference beam is spread by a lens and aimed via mirror directly at the film, while the object beam is spread and aimed at the object to be holographed. Because the object reflects some of the light onto the holographic film plate, the two beams interact, forming an interference pattern on the film. This pattern is the hologram. When the hologram is illuminated from the original direction of the reference beam, a 3D image of the object appears where the object was originally. WHAT'S HOLOGRAPHY USED FOR?  •• holographic art •• diffractive optics  •• security against forgery (e.g., credit card) •• holographic interferometry, for measuring changes in the dimensions of an object •• combining CAT scans into a 3D image •• holographic computer memory storage http://www.powertechnology.com/ Guillermo Alejandro Luque Terán Comunicaciones de Radio Frecuencia (CRF)