Light interaction with chemical

The chemical constitution of matter comprises both the geometrical structure and the forces acting between the atoms, and also the properties of the molecule or the crystal in the ground state and the interaction with chemical reagents and light. 

The ability of ultraviolet (UV) light to interact with chemicals was known and reported by Scheele in 1777 (1). Ritter in 1801 (2), Davy in 1812 (3), and Becquerel 1868 (4) reported similar results. 

Raman spectroscopy is an inelastic scattering technique that probes the vibrational energy levels within molecules and was first reported by C.V. Raman, who was awarded the Nobel Prize in Physics in 1930 for his discoveries. Nowadays, Raman spectroscopy is an established technique and is regularly used to analyze chemicals and materials, often in combination with infrared absorption spectroscopy since the two techniques are mutually complementary, that is, vibrational transitions that are Raman active are not IR active. In Raman scattering, light interacts with a molecule... 

Both extrinsic- and intrinsic-type sensors incorporate a transducer element making it an active device. Extrinsic sensors have an external transducer, and the optical fiber just serves the purpose of a light carrier to and from the external transducer whereas, intrinsic sensors have the structure of the optical fiber modified to incorporate the transducer element. In both cases, the transduction mechanisms change the light properties based on interaction with chemical species. 

The microscope has been associated with forensic science ever since Locard and Sherlock Holmes. The study of microscopy provides a foundation for study of spectroscopy. Simple microscopy is based on the interaction of visible light with matter, whereas spectroscopy is broadly defined as the interaction of electromagnetic energy with matter. Once visible light interacts with a sample, that light carries information about the physical and chemical characteristics of the sample. The same is true in all modes of spectroscopy. The detector in a microscope is the human eye and the characteristic that is most studied is color, but color is an expression of frequency and wavelength, characteristics exploited across the electromagnetic spectrum. 

The NIR spectrum contains information about the major X—H chemical bonds in an agricultural product. The spectrum by definition is dependent on all the functional groups that absorb NIR radiation, which in turn are correlated to the major chemical, physical, and/or sensory components of a substance. The spectrum also contains all of the information due to light interaction with the sample as well as instrumental artifacts, and data collection and computational errors. 

Surface photochemistry can drive a surface chemical reaction in the presence of laser irradiation that would not otherwise occur. The types of excitations that initiate surface photochemistry can be roughly divided into those that occur due to direct excitations of the adsorbates and those that are mediated by the substrate. In a direct excitation, the adsorbed molecules are excited by the laser light, and will directly convert into products, much as they would in the gas phase. In substrate-mediated processes, however, the laser light acts to excite electrons from the substrate, which are often referred to as hot electrons . These hot electrons then interact with the adsorbates to initiate a chemical reaction. 

Dmg receptors are chemical entities which are typically, but not exclusively, small molecules that interact with cellular components, frequently at the plasma membrane level (1,2). There are many types of receptors heat, light, immune, hormone, ion channel, toxin, and vims are but a few that can excite a cell. The receptor concept can be appHed generally to signal recognition processes where a chemical or physical signal is recognized. This recognition is translated into response (Fig. 3) and the process can be seen as a flow of information. 

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