The first light atomic nucleus from "second face"
When the nucleus of an atom is excited, its shape can change for a very brief moment. So far, this phenomenon has been observed in the most massive elements. Finally, however, researchers – including those from Poland – have managed to observe "second face" light atomic nucleus.
To some approximation, atomic nuclei look like spheres, in most casesoin more or less distorted. When the nucleus is excited, its shape can change, but only to the extreme krot a short while, then return to its original state. Atomic nuclei can change swoj shape depending on the amount of energy they have or the speed at which they rotate. Changes related only to the addition of energy (and therefore without taking into account rotationo(w) are sometimes relatively stable only in the nuclei of the most massive elementsow.
Now it turns out that the nuclei of the elementaloin much lighter ones, such as nickel, roalso may stagnate a bit longer in its new shape. The discovery was made by the teamoł scientistow from Italy (UniMi), Poland (Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow), Romania (IFIN-HH), Japan (University of Tokyo) and Belgium (University of Brussels).
The calculations necessary for the preparation of the experiment turned out to be so complex that a computer infrastructure of about a million processors had to be used to carry them outow. The effort has not been in vain: a publication describing the achievement has been rro¯ by the editoroin a prestigious physics journal „Physical Review Letters”. The research was announced by representatives of the IFJ PAN in a message sent to PAP.
Most atomic nuclei are more or less deformed structures, flattened or elongated along one, twooch, and often even all three axes. Moreover, just as a ball flattens more or less depending on the force exerted on it by the hand, atomic nuclei can change their deformation depending on the amount of energy they have, even when they are not spinning.
– When an atomic nucleus is supplied with an appropriate portion of energy, it can transition to a state with a different shape deformation than the typical one of the ground state. Such a new deformation – mofiguratively speaking: the new face – is, however, very impermanent. Like a ball when pushed back by a hand, ktorą it previously distorted, so the nucleus returns to its original form, only that it does so much, much faster, in times on the order of billionths of a billionth of a second or even krotier. Instead of o "second face" atomic nuclei, so it is probably better to mow here only about "grimoire" – describes Prof. Bogdan Fornal (IFJ PAN).
In the last few decades, evidence has been gathered that in the nuclei of a small number of elementsow occurs, however, a relatively stable state with a deformed shape.
Measurements have shown that the nuclei of someorych actinideow – elementow with atomic numbers from 89 (actinium) to 103 (lorens) – Are able to maintain their „second face” even tens of millionsoin times longer than the other nuclei. Actinides are elements with a total number of protonow and neutronoIn much more than 200, and therefore very massive. Amongrod of non-rotating elemental nucleioIn the lighter ones so far never observed excited state with deformed shape, characterized by increased stability.
Prof. Fornal with prof. Michel Sferrazza (University of Brussels) already three decades ago zwrociliated that the theory allows that in nuclei of elementaloin light there were stable states deformed by shape. Their attention was caught by nickel-66.
It was only recently, however, that an experiment in this area was realized. At the Bucharest gas pedal, the nickel-64 target was fired with oxygen-18 nuclei. During these collisions can form nickel-66, ktorgo nucleus in its basic shape resembles an almost perfect sphere. With properly selected collision energies, a small part of the Ni-66 nuclei formed in this way ends up in a certain state with a deformed shape, whichory – as measurements have shown – proved to be slightly more durable than all other stateoIn the excitations associated with significant deformation. In other words, the nucleus has reached a local deep minimum of potential.
– The extension of the lifetime of the state with the deformed shape of the Ni-66 nucleus, which we measured, is not as spectacular as in actinidesoin which dozens ofoin a millionow times. We registered an increase of only five times. Nevertheless, the measurement turned out to be exceptional anyway, because among theod of light nuclei is the first observation of this type,” concludes Prof. Fornal.
Pictured is the interior of Romania’s IFIN-HH accelerator facility, where the observations were made.