Electron-capture decay

Thus EC decay is favored for high Z nuclei. Of course, the decay energy must be greater than 1.02 MeV for 3+ decay, a situation found mostly in low Z nuclei where the slope of the walls of the valley of (3 stability is large (see Fig. 2.8) and decay energies of 1.02 MeV occur. 

Electron capture decay produces a vacancy in the atomic electron shells and secondary processes that lead to filling that vacancy by the emission of X-rays and Auger electrons occur. These X-rays permit the detection of EC decays. 

In EC decay, the chemical effects of the X-ray intensity ratio KJK was first observed by Tamaki et al. for various chromium compounds labeled with Cr. A Si(Li) detector was used to measure the X-rays emitted from the nuclide. When the measured data of K, /K, are plotted against the formal oxidation number of diromium, it is seen that the ratio generally increases with the chromium valence number. This is shown in Fig. 2. A notable exception is, however, metallic chromium, where the formal oxidation number does not reflect the electronic state surroimding the chromium atom at all. 

Lazzarini et al. also studied the chemical effect on the X-ray intensity ratios in chromium compounds labeled with Cr or in Cr-doped materials. They pointed out that the intensity ratio might be influenced by factom such as crystal parameters of the matrix surroimding the decaying atom. They also performed similar experiments for Fe-labeled compounds and for Fe-doped crystals, md found chemical effects on the X-ray intensity ratio K /K, in these cases as well. 

As to manganese which is just between chromium and iron in the periodic table, it is not surprising that its K /K X-ray intensity ratio increases with increasing formal oxidation number still, only a sli t effect was found 

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Mass-spectroscopic technique has also been used with non-fissile targets after pile or cyclotron bombardment to determine the mass-numbers of radioactive nuclides. In one case, the branching ratios of certain isotopes for and electron capture decay (where different elements are produced by the two routes) were determined from the amount of the stable end-products of radioactive decay, using the mass-spectrometer to identify the isotopes concerned and to correct for any stable impurities of the elements concerned (98). For some purposes, mass-spectroscopic separations could be very valuable technically such as the... 

To complete our survey of the energy release in (3 decay, let us consider the case of electron capture, that is, the electron capture decay of Bi e + Bi —> 207Pb + re + energy. For the energy release in the decay, we have... 

Beta decay is a general term applied to radioactive decay processes that result in the mass number A remaining constant while the atomic number Z changes. There are three types of beta decay beta-minus (/3 ) decay, positron (/3+) decay, and electron capture decay. It should be mentioned that (3 decay is often referred to as just beta decay, which is not strictly correct, because it is only one type of beta decay. 

Electron Capture Decay. Electron capture decay is a competing process to positron decay and thus results in an increase in the neutron-to-proton ratio in the nucleus. In this process, a bound, inner orbital electron is captured by the nucleus, resulting in the conversion of a proton into a neutron, the emission of a neutrino, and, if the daughter nucleus is left in an excited state, the emission of one or more gamma rays. The net reaction is shown below ... 

Beta-Minus Decay 370 Positron Decay 3 72 Electron Capture Decay 3 72 Gamma Ray Emission 373... 

Figure 1. Decay scheme of 195Au and energy level diagram of 195Pt (10). represents the relative transition probability for electron capture decay to the state i in 195Pt and P /Pj is the ratio of K to total capture for decay to the state i.

He is produced by decay of tritium generated from the neutron activation of Li and " °Ar is produced by electron capture decay of Of the xenon isotopes, Xe is produced by the spontaneous fission of and Xe is produced by beta decay of Isotopes of neon and other isotopes of argon and xenon are produced by a variety of other nuclear reactions. 

Electron capture decay (EC). The nucleus captures an electron from the electron cloud of the atom (mainly the K shell), and a proton becomes a neutron. 

K0 IK a x-ray intensity ratios in 3d elements by photoionization and electron-capture decay... 

The K0 IKa x-ray intensity ratios by photoionization and electron-capture decay have been calculated for several chemical compounds of 3d elements by the use of the discrete-variational Xo (DV-Xa) molecular orbital method. The calculated results indicate that the K/3lKa ratios depend on the excitation mode as well as the chemical effect. For the similar chemical environments the K0 /Ka ratio by photo ionization is larger than that by electron-capture decay, due to the excess 3d electron in the latter case. However, the difference is small, sometimes negligible in comparison with the chemical effect. Possible reasons for large difference in earlier experiments are discussed and future experiments are suggested. 

KEYWORDS K/3lKa ratio, electron-capture decay, photoionization Corresponding author, e-mail mukoyama elec.kuicr.kyoto-u.ac.jp... 

However, Hansen et al. (5) measured -x-ray intensity ratios following A -capture decay of radioactive nuclei and pointed out that there is considerable difference between K/3 IKa ratios by electron-capture decay and those by x-ray or electron bombardment. Later, Paic and Pecar (6) found that the K/3 IKa x-ray intensity ratios for 3d transition elements depend on the mode of excitation. The K0/Ka ratios by electron-capture decay (EC) are smaller by almost ten per cent for Ti, V, Cr, and Fe than those by photoionization (PI). However, no appreciable difference was observed for Cu and Zn. A similar experiment was performed for Mn by Arndt et al. (7). They pointed out that the reason for this difference is due to the 3d excess electron in EC and the strong shakeoff process accompanying PI. Tamaki et al. (8) measured the K/3/Ka ratios for various chemical compounds of V, Cr, and Mn excited by PI and EC. 

Neutrino (v). A particle of no charge and mass emitted with variable energy during / + and electron capture decays of radionuclides. 

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