Electromagnetic radiation spectroscopy with

In spectroscopy we study the effect of interaction of electromagnetic radiation on matter. For examples X-rays are produced by bombandment of metal targets with high speed electrons. So the different types of electromagnetic radiation interact with the matter and give different types of spectroscopy. 

The science known as spectroscopy is a branch of physics that deals with the study of the radiation absorbed, reflected, emitted, or scattered by a substance. Although, strictly speaking, the term radiation only deals with photons (electromagnetic radiation), spectroscopy also involves the interactions of other types of particles, such as neutrons, electrons, and protons, which are used to investigate matter. 

Today, organic chemists rely on an array of very powerful instruments that enable them to identify compounds in much less time. With use of these instruments, it is often possible to determine the structure of an unknown compound in less than an hour. Three of the most powerful techniques are presented in this and the following chapters. They are infrared spectroscopy and two related techniques proton and carbon-13 nuclear magnetic resonance spectroscopy. Spectroscopy is the study of the interaction of electromagnetic radiation (light) with molecules. 

Spectroscopy (Chapter 13) The study of the interaction of electromagnetic radiation (light) with molecules. 

Concentrating on metalloenzymes, we have developed a strategy based on stopped flow X-ray absorption spectroscopy (XAS) to elucidate in detail the molecular mechanisms at work during substrate turnover (Fig. 4). Importantly, XAS provides local stmctural and electronic information about the nearest coordination environment surrounding the catalytic metal ion within the active site of a metalloprotein in solution. When the X-rays hit a sample, the electromagnetic radiation interacts with the electrons bound in the metal atom. The radiation can be scattered by these electrons, or it can be absorbed, thereby exciting... 

Very detailed information about structure is obtained from investigations in which electromagnetic radiation interacts with matter. An important area of study, known as spectroscopy, is concerned mainly with the extent to which substances absorb radiation at various wavelengths. The information obtained through spectroscopy has contributed greatly to our understanding of chemical structure and is particularly important in biology. 

The interaction of light and molecules forms the basis of IR spectroscopy. Here it will be given a short description of the Electromagnetic Radiation, the energy levels of a molecule and the way the Electromagnetic Radiation interacts with molecules and their structure [5,6]. 

Figure 1 The regions of the electromagnetic spectrum. The wavenumber, wavelength, frequency, and energy are the characteristics that describe electromagnetic radiation. (Reprinted with permission from Banwell C and McCash E (2003) Fundamentals for Molecular Spectroscopy. 4th edn. London McGraw Hill The McGraw-Hill Companies, Inc.)...

Most of our knowledge about the structure of atoms and molecules is based on spectroscopic investigations. Thus spectroscopy has made an outstanding contribution to the present state of atomic and molecular physics, to chemistry, and to molecular biology. Information on molecular structure and on the interaction of molecules with their surroundings may be derived in various ways from the absorption or emission spectra generated when electromagnetic radiation interacts with matter. 

The spectroscopy of solids is defined as the qualitative or quantitative measurement of the interaction of electromagnetic radiation (emr) with atoms or molecules in the solid state. The emr interacts as scattering, absorption, reflectance, or emission with solid matter. A variety of spectrometer configurations are used to optimize the measurements of electromagnetic radiation as it interacts with solid matter. This chapter provides an overview of... 

Up to this point, the wavefunctions considered do not evolve with time. In some cases, the Hamiltonian may have time-dqtendent terms indicating that the system changes with time. An important example is when electromagnetic radiation interacts with a system. Electromagnetic radiation consists of electric and magnetic fields that oscillate in space and time. When electromagnetic radiation interacts with a molecule (such as in spectroscopy), the oscillating fields will result in a time-dependent element in the complete Hamiltonian for the molecule. As already observed in the case of infrared spectroscopy, this interaction may result in a transition of states. 

As discussed in more detail elsewhere in this encyclopaedia, many optical spectroscopic methods have been developed over the last century for the characterization of bulk materials. In general, optical spectroscopies make use of the interaction of electromagnetic radiation with matter to extract molecular parameters from the substances being studied. The methods employed usually rely on the examination of the radiation absorbed. 

As diverse as these techniques are all of them are based on the absorption of energy by a molecule and all measure how a molecule responds to that absorption In describing these techniques our emphasis will be on then application to structure determination We 11 start with a brief discussion of electromagnetic radiation which is the source of the energy that a molecule absorbs m NMR IR and UV VIS spectroscopy... 

In the previous section we defined several characteristic properties of electromagnetic radiation, including its energy, velocity, amplitude, frequency, phase angle, polarization, and direction of propagation. Spectroscopy is possible only if the photon s interaction with the sample leads to a change in one or more of these characteristic properties. 

In absorption spectroscopy a beam of electromagnetic radiation passes through a sample. Much of the radiation is transmitted without a loss in intensity. At selected frequencies, however, the radiation s intensity is attenuated. This process of attenuation is called absorption. Two general requirements must be met if an analyte is to absorb electromagnetic radiation. The first requirement is that there must be a mechanism by which the radiation s electric field or magnetic field interacts with the analyte. For ultraviolet and visible radiation, this interaction involves the electronic energy of valence electrons. A chemical bond s vibrational energy is altered by the absorbance of infrared radiation. A more detailed treatment of this interaction, and its importance in deter-... 

Spectroscopy is basically an experimental subject and is concerned with the absorption, emission or scattering of electromagnetic radiation by atoms or molecules. As we shall see in Chapter 3, electromagnetic radiation covers a wide wavelength range, from radio waves to y-rays, and the atoms or molecules may be in the gas, liquid or solid phase or, of great importance in surface chemistry, adsorbed on a solid surface. 

Spectrometers are designed to measure the absorption of electromagnetic radiation by a sample. Basically, a spectrometer consists of a source of radiation, a compartment containing the sfflnple through which the radiation passes, and a detector. The frequency of radiation is continuously varied, and its intensity at the detector is compar ed with that at the source. When the frequency is reached at which the sample absorbs radiation, the detector senses a decrease in intensity. The relation between frequency and absorption is plotted as a spectrum, which consists of a series of peaks at characteristic frequencies. Its interpretation can furnish structural information. Each type of spectroscopy developed independently of the others, and so the data format is different for each one. An NMR spectrum looks different from an IR spectrum, and both look different from a UV-VIS spectrum. 

Much of our knowledge of molecules is obtained from experimental studies of the way they interact with electromagnetic radiation, and the recent growth in non-linear spectroscopies and molecular electronics has focused attention on our ability (or otherwise) to predict and rationalize the electric properties of molecules. The idea of an electric multipole is an important one, so let s begin the discussion there. 

Problem 14.13 Calculate the energy range of electromagnetic radiation in the UV region of the spectrum from 200 to 400 nm. How does this value compare with the values calculated previously for IR and NMR spectroscopy ... 

How do we know the composition of the sun and other stars How can we measure the temperature inside a flame so hot that any thermometer would melt How can we explore chemical reactions among molecules that are much too tiny to see directly Light allows us to do all these things. The study of matter with electromagnetic radiation is called spectroscopy. 

Spectroscopy The science of analyzing the spectra of atoms and molecules. Emission spectroscopy deals with exciting atoms or molecules and measuring the wavelength of the emitted electromagnetic radiation. Absorption spectroscopy measures the wavelengths of absorbed radiation. 

The physical basis of spectroscopy is the interaction of light with matter. The main types of interaction of electromagnetic radiation with matter are absorption, reflection, excitation-emission (fluorescence, phosphorescence, luminescence), scattering, diffraction, and photochemical reaction (absorbance and bond breaking). Radiation damage may occur. Traditionally, spectroscopy is the measurement of light intensity... 

The field of science that studies the interaction of electromagnetic radiation with matter is known as spectroscopy. Spectroscopic studies on the wavelength, the intensity of the radiation absorbed, emitted, or scattered by a sample, or how the intensity of the radiation changes as a function of its energy and wavelength, provide accurate tools for studying the composition and structure of many materials (Davies and Creaser 1991 Creaser and Davies 1988). 

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