Spectrum of radiation

Optical background, n - the spectrum of radiation incident on a sample under test, typically obtained by measuring the radiation transmitted through or reflected from the spectrophotometer when no sample is present, or when an optically thin or non-absorbing standard material is present. 

The absorption spectrum of radiation-produced eam is identical to that in dilute metal-ammonia solutions. It has a broad, structureless absorption in the red and IR, with a peak at about 1.88 pm and a half-width of 0.2 eV on the high-energy side. The absorption is intense with max = 4.8 x 104 M 1cm 1, giving an... 

Black-body radiation is the radiation emitted by a black-colored solid material, a so-called black body, that absorbs and also emits radiation of all wavelengths. A black body emits a continuous spectrum of radiation, the intensity of which is dependent on its wavelength and on the temperature of the black body. Though a black body is an idealized system, a real solid body that absorbs and emits radiation of aU wavelengths is similar to a black body. The radiation intensity of a black body, at... 

Figure 3 Left Optical absorption spectrum and STM image of radiation-induced oligomers Agv at partial reduction and stabilized by PA [85,86]. Right Absorption spectrum of radiation-induced silver clusters Ag in the presence of EDTA. (a) After partial reduction (10 krad), (b) after 4 days, (c) after 8 days. Inset TEM micrographs of (a), (b), (c), and electron diffraction pattern of sample c. (From Ref 145.)...

ATOMIC SPECTRA. An atomic spectrum is the spectrum of radiation emitted by an excited atom, due to changes within the atom in contrast to radiation arising from changes in the condition of a molecule. Such spectra are characterized by more or less sharply defined lines," corresponding to pronounced maxima ai certain frequencies or wavelengths, and representing radiation quanta of definite energy. 

Most atmospheric visible and DV absorption and emission involves energy transitions of the outer electron shell of the atoms and molecules involved. The infrared spectrum of radiation from these atmospheric constituents is dominated by energy mechanisms associated with the vibration of molecules. The mid-infrared region is rich with molecular fundamental vibration-rotation bands. Many of the overtones of these bands occur in the near infrared. Pure rotation spectra are more often seen in the far infrared. Most polyatomic species found in the atmosphere exhibit strong vibration-rotation bands in the 1 - 25 yin region of the spectrum, which is the region of interest in this paper. The richness of the region for gas analysis... 

Bob speaks into the flexscreen, Brunhilde, show solar spectrum, and the screen displays figure 2.3. Our Sun emits a wide spectrum of radiation that peaks in the yellow range of the spectrum. On the flexscreen, you see a radiation curve for the Sun and the wavelengths at which the Sun radiates most intensely. ... 

The intensity and penetrating power of the mercury radiation projected in the direction of motion of the electrons and also perpendicular to it have been measured by means of the ionizing effects produced inside of the ionization chamber. These experiments have been made in order to determine whether or not the beams of rays are homogeneous, and, also, to compare the penetration with that to be expected according to certain theoretical distributions of energy in the spectrum of radiation due to the impacts of electrons of given velocity. The material used to de-... 

The spectrum of radiation from electronically excited states of atoms appears as lines, when the emission from a hot gas is diffracted and photographed, whereas radiation from these excited states of molecules appears as bands because of emission from different vibrational and rotational energy levels in the electronically excited state. Equation (26) shows that the intensity of radiation from a line or band depends upon the temperature and concentration of the excited state and the transition probability (the rate at which the excited state will go to the lower state). Since the temperature term appears in the exponential, as the temperature rises the exponential term approaches unity, as does the ratio of the concentration of the excited (emitting) state to the ground state (as T approaches oo, Ng = Nj). The concentrations of both the ground and excited states, however, reach a maximum, and then decrease due to the formation of other species. The line or band intensity must also reach a maximum and then decrease as a function of temperature. This relationship can be used to determine the temperature of a system. 

Radiation induced changes in the electronic structure of all samples were evident as changes in energy loss spectrum with increased exposure to the electron beam. The spectrum of radiation induced chromophores could thus be studied (1 ). Spectra recorded at the earliest exposure times compared favorably with optical results and are believed to contain primarily intrinsic electronic excitations (1, 2, 4). An analysis of these intrinsic spectra is the subject of the bulk of this paper. The spectra of radiation damaged polymers are described briefly after the intrinsic excitations are discussed. 

Many quality assurance procedures in diagnostic radiology require the use of a phantom to simulate the X-ray attenuation of the patient. The phantom should transmit the same quantity and quality (i.e. spectrum) of radiation as that transmitted by the patient. The knowledge of photon spectra at the position of measurement on the surface, inside and behind standard dosimetric and imaging phantoms is helpful for performing dosimetric or calibration measurements and hence helpful in the course of quality control. The experimental approach is limited however, simulation with Monte Carlo methods has been proved to be a very powerful technique (Petoussi et al., 1992). 

We are going to give the frequency spectrum of radiation and explain the natural width of the spectrum line. As an atom emits photons, its energy drops and the amplitude of transition decreases over time. Therefore, the emission is not harmonic, and a spectrum occurs. We shall see that the natural width of the spectral line can be connected to the attenuation coefficient of the damped oscillator. Inversely, from the width of the spectral line, we might determine the attenuation coefficient of the oscillator. 

Switzerland, yielded the spectrum reproduced in Fig. 5.40. The numerical values upon which this diagram is based can be found in M. Iqbal [5.34]. The maximum of EfAn lies in the visible light region at A pa 0.45 /tm. 99 % of the irradiance falls in the wavelength band A < 3.8 fim. Fig. 5.40 also shows the spectral irradiance EXa of the radiation emitted by a black sun at Ts = 5777 K. The areas under the two curves (up to A —> oo) are equal — they each yield the solar constant E0 —, but the spectrum of the extraterrestrial solar radiation deviates significantly at some points, in particular at A < 0.6//.in, from the spectrum of radiation from a black body. 

In 1900 Planck derived an empirical relationship for data from a black body radiation by introducing a concept of quantisation of energy he was able to prove the relationship theoretically. It had been shown that at a specific temperature the spectrum of radiation from a black body was unparalleled in its characteristics and the energy varied... 

We now examine the spectrum of radiation phase constructed in the preceding subsection. Consider the state... 

Indeed, it was Maxwell s generalization of the laws of electrodynamics that revealed that the radiation solutions of these equations, which would not have appeared in the earlier version (without the displacement current term) predicted all the known optical phenomena. After Maxwell s investigation of these optical implications of electrodynamics, other portions of the spectrum of radiation solutions were predicted and discovered empirically radiowaves, X- rays, infrared radiation, and gamma rays. Thus, it was Maxwell s intuitive feeling for the need of symmetry in his laws of electrodynamics that led to the full unification of electrodynamics and optics in the expression of Maxwell s equations. 

This type of instrument is highly sekciivc because healing of the sensor gas occurs only from that narrow portion of the spectrum of radiation absorbed by the earbon monoxide in the sample. The device can be adapted to the determination of any IR-absorbinggas. 

The emission spectrum of a body or substance is the characteristic range of radiations it emits when it is heated, bombarded by electron or ions, or absorbs photons. The absorption spectrum of a substance is produced by examining, through the substance and through a spectroscope, a continuous spectrum of radiation. The energies removed from the continuous spectrum by the absorbing medium show up as black lines or bands. With a substance capable of emitting a spectrum, these are in exactly the same positions in the spectrum as some of the lines and bands in the emission spectrum. 

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