拉曼光谱raman Spectroscopy.pptVIP

Raman Spectroscopy Anatasia Gangadin Dr. Ronald Birke City College of New York What is Spectroscopy? The study of how species (i.e., atoms, molecules, solutions) react to light. Some studies depend on how much light an atom absorbs. The electromagnetic radiation absorbed, emitted or scattered by the molecule is analyzed. Typically, a beam of radiation from a source such as a laser is passed through a sample, and the radiation exiting the sample is measured. Some, like Raman, depend on a molecules vibrations in reaction to the light. Sir Chandrashekhara Venkata Raman SERS vs. Raman During charge transfer, some vibrations will be altered due to a molecules interaction with the surface, resulting in some of the SER bands being shifted in respect to the normal Raman Spectrum. SER spectra of a different small peptides and proteins were obtained from a roughened surface using a Raman spectrometer. Why Raman? In Raman spectroscopy, by varying the frequency of the radiation, a spectrum can be produced, showing the intensity of the exiting radiation for each frequency. This spectrum will show which frequencies of radiation have been absorbed by the molecule to raise it to higher vibrational energy states. What Exactly Is Being Measured? Stokes vs. Anti Stokes Atoms are at a certain energy level at any given time. As a laser light hits the atom, it is excited and reaches a higher level of energy, and then is brought back down. If an atom is at a given energy level, it can be excited then fall below the original level. Anti-stokes spectrum are mirror spectrums of Stokes Raman Spectrums Using Stokes/Peaks to Determine Vibrations How To carry Out a Raman Experiment Raman Instruments Results of Other Raman Studies Proposing a Structure Histidine One of the common natural amino acids. Nutritionally, histidine is considered an essential Amino Acid, but mostly only in children. In Catalytic Triads, the basic nitrogen of histidine is used to extract a proton from Serine, Threo