}

How long do electrons live?

2003/12/01 Andonegi Beristain, Garazi - Elhuyar Zientziaren Komunikazioa Iturria: Elhuyar aldizkaria

Gold, silver and copper are precious metals. But how long do electrons live in these metals?

This is one of the questions asked by the Department of Physics of Condensed Matter of Leioa. In fact, they seek theoretical models and formulas to describe the characteristics and behavior of noble metals. These theoretical calculations are of great importance since according to the results the new applications for these materials will be selected.

Periodic structure of metals

In gold, silver and all metals in general, atoms form a periodic net. Around this periodic network is the electron cloud, which is also dynamic. Electrons move and interact within this cloud.

/></div> <p>In Leioa they investigate theoretical formulas to describe the electronic structure of gold, silver and copper, among others. (Photo: www.nsrw.com).</p> <p>Until now, when the characteristics of the metals have been theoretically calculated, the periodic network of atoms has been assimilated to a homogeneous surface. Although this theoretical approach explained the electronic behavior of several materials, in other materials there used to be great differences between the theory and the results obtained experimentally.</p> <p>For this reason, in recent years new theoretical formulas based on more real models have been invented. In these realistic models the true structure of the atoms is accepted to perform the calculations — that is, the periodic net is not matched with a homogeneous surface— and the interactions between the electrons are taken into account (for example, hole of correlation and exchange). All this, although it makes the calculation very difficult, leads to results closer to reality.</p> <h2>Life time of excited electrons</h2> <p>In these theoretical calculations the life time of excited electrons is analysed. Excited electrons are electrons that have received energy. Because of this energy, they leave their basic energy level stable and jump to another higher energy level. These electrons tend, therefore, to return to the basic stable level, for which they must lose the energy they have received. They lose this energy by giving in to another or other electrons.</p> <p>The time it takes an excited electron to return to its basic level (1 fs = 10<sup>-15</sup> s) is representative of the electronic structure of the material.</p> <p>If the electron takes a long time to return to the basic energy level, this indicates that the rest of the electrons in the metal structure are energetically removed. In these cases, the excited electron is made it difficult to transfer the excess energy to another electron, which leads it to stay longer excited. This indicates that in the metal structure most electrons are in a low stable energy level, indicating that the basic energy level of electrons is low.</p> <p>On the contrary, if the life time is short, it means that the basic energy level of the electrons is high and, therefore, they will be easily exchangeable.</p> <p>Therefore, depending on the time of life, it is possible to know the energy level of the electrons in the metal structure. Therefore, the calculation of the life time of electrons is a step to know the electronic structure and behavior of materials.</p> <ul> <li><strong>Project title</strong><br />Quadratic response and effects of N bodies in solids.</li> <li><strong>Objective</strong><br />Study of the life times of excited electrons in solids and description of interactions between charged particles and surfaces.</li> <li><strong>Director</strong><br />J.M. Pitarke.</li> <li><strong>Workforce</strong> <br />A. Bergara, A. Garcia-Lekue, M. Garcia-Vergniory, I. G. Gurtubay, T. Del Río.</li> <li><strong>Department</strong><br />Department of Condensed Matter Physics.</li> <li><strong>Faculty</strong><br />Faculty of Science and Technology.</li> <li><strong>Financing</strong><br />CYCIT.</li> </ul> </div> </div> <div class=
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