X- and 7-rays

X- and 7-rays are exponentially absorbed and the intensity I at any distance x in an absorbing medium is given by 

The energy effectively used is, however, less than the energy lost from the primary beam, part of it being diverted to scattered radiation. Therefore total energy absorption coefficients, pa and pa /p, which are less than the corresponding p and p/p, have been defined. It is very important to avoid confusion between these coefficients this is not always easy owing to the diversity of symbols used in the literature. 

There are various mechanisms of interaction of radiation with matter. These are 

Each of these is characterized by a mass attenuation coefficient which are, respectively, r/p, o/p and zc/p. To each there is a corresponding total energy absorption coefficient. The mass attenuation and absorption coefficients for aluminium and water are given in Fig. 1. 

When an X- or 7-quantum collides with an atom, all the energy of the incident photon is transferred to an electron of the atom according to 

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It is understandably impossible to separate x-rays and 7-rays on a wavelength scale. 7-Rays have energies from 104 to 107 ev hence their wavelengths range from about 1 to about 0.001 A (Equation 1--2). 

Figure 10 Changes in the X-ray and 7-ray luminosity above 5 keV is shown by the dashed line. The associated changes in the optical bolometric luminosity (dashed) are compared with the energy generation rate due to 56Co decay (solid line).

As the column depth of the supernova ejecta decreases as t 2, 7-rays and hard X-rays suffer from less Compton scattering and photoelectric absorption and eventually emerge from the surface. The timing of their emergences and light curves are sensitive to E, Menv, and the distribution of elements. In other words, X-ray and 7-ray observations provide another good diagnosis of the supernova interior. 

Finally, we tried a numerical experiment where 56Ni exists only in the outermost 0.2 M layer beneath the surface. The escape of X-rays and 7-rays are significant and the resulting optical light curve (the dash-dotted curve in Fig. 11) is as narrow as SN 1964L. Such a composition inversion is not realistic for helium stars but a natural outcome from the off-center detonation in accreting white dwarfs. 

Mixing of 56Co into hydrogen-rich envelope may be required to account for the optical light curve and the early emergence of X-rays and 7-rays. Mechanism of mixing needs to be explored. 

X-rays and 7-rays from Supernova 1987a P. Sutherland1, Y. Xu2, R. McCray2, and R. Ross3 SUMMARY... 

Figure 1 X-ray and 7-ray fluxes for Model 10H (no mixing). The numbers (with the solid curves) indicate the energy bands in keV the dotted curve is for the 7-ray line at 847 keV and the dashed curve is for the Fe Ka line at 6.4 keV. The 5

Figures la, b show the hard X-ray and 7-ray spectra for the above model at t — 200 and 250 d as compared with the Ginga and Kvant observations at i = 200 d and the balloon borne observations (Wilson et al. 1988) at i = 250 d. The calculations clearly show that the spectrum becomes harder as the ejecta expands and the number of Compton scattering decreases. The power law spectra, E a, at 30 - 200 keV with the index a 1.3 (200 d) and 1.1 (250 d) are in reasonable agreement with observations.

As a prediction for future observations, X-ray and 7-ray spectra at t = 400 d and 600 d are shown in Figures lc, d. The spectrum will become harder as the column depth of the ejecta decreases. Comparison with the observations will inform us more detailed abundance distribution and the dumpiness of the ejecta. 

Figure 1 The calculated hard X-ray and 7-ray spectra for the the hydrodynamical model with E = 1 xlO51 erg and Menv = 6.7 M0 at a) t = 200 d, b) i = 250 d, c) t = 400 d, and d) t = 600 d. At t = 200 d, the crosses indicate the spectrum observed by Ginga and the open circles and the diamonds are obtained by Kvant. At t = 250 d, balloon-borne observation (Wilson et al. 1988) is shown.

IV. Irradiation of Starch with Neutrons, X-Rays, High-Energy Electrons, and 7-Rays... 

In addition to well-recognized cationic initiators for the solution polymerization of acetaldehyde (50, 51, 52) more specialized systems for preparing elastomeric polyacetaldehyde have been uncovered. They include the polymerization of acetaldehyde by condensing the monomer onto 7-alumina (17, 18, 19, 21) from the vapor phase or polymerization with acid-treated oxide supports (43, 54), the use of phosphines (20) as initiator and polymerization by x-rays (41) and 7-rays (8). 

Certain monomers crystallize in a conformation such that they can be zipped together without changing the symmetry of the crystal lattice. In the crystalline state, the arrangement of monomers is. strictly determined by crystal packing. Polymerization is usually initiated by irradiation with UV, X- or 7-rays and is assumed to proceed by a radical mechanism. For example, muconic acid esters (25, 2 7, 29) and ammonium salts (2 6, 2 8,30) can be stcrcospccifically polymerized in the crystalline state to high conversion.""" "" "" This form of... 

The purpose of this chapter is to review and assess the various approaches that have been used to study the radiation-induced decomposition processes in the azides with the hope of giving a clear picture of the state of the art. While the effects of both electromagnetic and particle irradiations have been investigated, most of the work reported in this chapter is concerned with the former, i.e., ultraviolet light and to a lesser extent visible light. X-rays, and 7-rays. This chapter is limited to those azides in which radiation-induced decomposition has been studied. 

Thermoluminescence measurements were also made on X-ray and 7-ray irradiated KN3 from 47 to 255°K, yielding activation energies and pre-exponential factors [74,75]. Because the heating rates are different from those used for the UV-irradiated KN3, it is difficult to relate the two sets of data. Since thermoluminescence is sensitive to impurity content, there are also problems in relating studies on crystals grown in different laboratories. However, Townsend et al. [74,75] determined pre-exponential factors which have also been obtained from kinetic studies of the decay of ESR and optical spectra, enabling a comparison with determinations from annealing studies of ESR and optical bonds. In X-ray... 

Primary explosives have been irradiated with electrons [14,105-107], neutrons [14,101], fission fragments [14,108,109], a-particles [100,110], X-rays [106], and 7-rays [111,112]. 

With atomic species, the near edge structure is of no further interest. With molecular adsorbates, the near edge X-ray absorption is dominated by intramolecular transitions (/X- and (7-resonances). Their dependency on the polarization provides information on the orientation of the molecule. From the energy of the a-resonance intramolecular bond lengths, tab can be estimated for simple molecules. Figure 5.97 shows an X-ray absorption spectrum of NO adsorbed on a nickel surface. 

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