Все науки. №6, 2022. Международный научный журнал - страница 25

Here it is important to define such a concept as the excitation energy of a composite nucleus, which was formed during the absorption of a free nucleon. It is the sum of the binding energy of the nucleons of the target nucleus and part of its kinetic energy (1).

Part of the kinetic energy due to the large difference in the masses of the nucleus and the nucleon in such cases becomes equal to the kinetic energy of the bombarding nucleon. On average, the binding energy is equal to 8 MeV and can change only with the distinctive features of the composite nucleus formed in this process, but for the precisely specified target nucleus and nucleon, this value is a constant. The kinetic energy of a particle can be anything, for example, in nuclear reactions where a neutron strikes, due to the fact that there is no repulsive force of the nucleus – the Coulomb barrier, their energy can be extremely close to zero.

Thus, the kinetic energy is the minimum excitation energy of the composite nucleus.

And it is from the statement of the presence of a composite nucleus and the existence of nuclear decay channels that we can conclude about the existence of reaction channels. The reaction channels themselves are the ways of transition from an excited to an unexcited state. The type and quantum state of the incoming particles and nuclei before the start of the reaction determine the input channel of the nuclear reaction, after the completion of the reaction, the totality of the formed particles, that is, the reaction products and their quantum state is determined by the resulting output channel of the reaction. The complete characterization of the nuclear reaction is carried out by input and output channels.

The composite nucleus itself lives for quite a long time, due to which the choice of the reaction channel itself does not depend at all on the method of formation of the composite nucleus, due to which it «forgets» how it was formed. This becomes the reason for the assertion of the independence of the processes of the organization of the composite core and its disintegration. A striking example can be the situation of the formation of an excited aluminum-27 nucleus in the following ways (2).

But it decays violently in the same way in all cases, provided that the excitation energy is the same. But at the same time, there is also a possibility of reverse decay of any of these reactions, with a certain probability that does not depend on the history of the origin of the excited nucleus itself. If we talk about the probability of such events, then the dependence becomes between the grade of the target nucleus and the energies.

As previously indicated, nuclear reactions can also proceed through a direct channel of interaction at high energies, since the nucleons of the nucleus can be considered as free. The difference from the previous composite core model from the direct reaction model initially consists in the distribution of the momentum vectors of the particles-products of the nuclear reaction, relative to the momentum of the bombarding particles. If spherical symmetry operates in the composite model, then in this case the geometry is simpler and the advantage in choosing the directions of the resulting particles is in the direction of the incoming particles.

Earlier, the concept of the probability of a nuclear reaction was mentioned, which is represented by a quantity called the effective cross section of a nuclear reaction. In the laboratory system of the report, the resting situation of the target nucleus is taken, the probability of interaction is determined by the product of the cross section by the flow of incident particles, while the cross section is expressed in units of area, and the flow in the number of particles crossing the unit area per unit time. The cross section of the nuclear reaction itself is calculated in extremely small units of area – barns equal to 10—24 cm