Nuclear charge rates

The expression for the rate R (sec ) of photon absorption due to coupling V beriveen a molecule s electronic and nuclear charges and an electromagnetic field is given through first order in perturbation theory by the well known Wentzel Fermi golden rule formula (7,8) ... 

The present status of the field effects may be summarized as follows both the high nuclear charge and paramagnetic effects seem to be well-established for spectroscopic transitions,449 463 but neither of them has been demonstrated unambiguously for radical reaction rates. 

The forbidden autoionization rates increase strongly with nuclear charge. As discussed above, we expect the width of (2p2)3Pj=0 and (2p2)3Pj=2 to scale as Z6 since they can mix with states formed from the same configuration that can autoionize nonrelativistically, while the width of (2p2)3PJ=1 is expected to grow as Z4. This is illustrated in Figure 5.10, which also shows that for Z = 20 the difference between forbidden and allowed transitions has vanished. 

Conceptually, it is the atomic number and the electronic configuration of an element that define its position in the Periodic Table. Since they cannot be measured for the very heavy elements, information on its chemical behavior is often used to place an element in a chemical group. Unfortunately, with increasing nuclear charge the cross sections and the production rates drop so rapidly that such chemical information can be accessed only for elements with a half-life of the order of at least few seconds and longer. In this case, some fast chemistry techniques are used. They are based on the principle of chromatographic separations either in the gas phase exploiting the differences in volatility of heavy element compounds, or in the aqueous... 

Paramagnetic relaxation reagents (pa.r.r.), such as Gd, Mn ", Cu ", and Cr ", and other paramagnetic metal ions with isotropic charge-distribution, affect the nuclear relaxation rates, T, and T2, of species under investigation by n.m.r. spectroscopy through electron-nuclear spin-spin coupling. There are two classes of pa.r.r.s which are characterized by the predominant mechanism of relaxation enhancement. 

Geiger and Marsden continued to study the deflection of a-particles, and in 1913 (after observing over 100,000 scintillations at a rate of 5 to 90 per minute) correlated nuclear charge with atomic number. In 1914 and 1915 Marsden continued to study the impact of a-particles on matter these experiments led to Rutherford s 1919 fortuitous attainment of the alchemist s dream the artificial transmutation of the elements. 

Enhancement of Nonradiative Decay. The proximity of a molecule containing an atom of high nuclear charge or unpaired spin may cause a dramatic enhancement of spin-forbidden nonradlatlve decay rates (13). The phenomenon is very well documented in small molecules - that is, nonpolymer photochemistry - but appears not to have been reported extensively in the polymer field. 

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