A NEW ELEMENT

Hawke's Bay Tribune, Volume XXIV, Issue 233, 14 September 1934, Page 14

A NEW ELEMENT

Fresh Outlook in Physics ITALIAN’S DISCOVERY Bombarding of Substances A few weeks ago the physicists of Europe were excited by private communications from Professor Enrico Fermi, in which he described remarkable results obtained by bombarding various atoms with neutrons. The interest of these results was heightened by the circumstance that Professor Fermi is the most distinguished Italian theoretical atomic physicist of the day, and the scientific world had not hitherto looked to him for experimental researches, writes the scientific correspondent of the “Manchester Guardian.” Professor Fermi has already announced that he has evidence of the production of forty-seven types of radioactive atoms obtained by bombarding atoms of phosphorus, iron, silicon, and many other common elements with beams of neutrons. Before making any comment on these results something should be said of the present state of experimental atomic physics. After the accomplishment of the first artificial disintegration of an atom by Rutherford in 1919 there was a quiet period in experimental atomic research. Investigators turned to the refinement of previous observations. 1960 a considerable amount of evidence of anomalous behaviour by atoms had been collected. Some radiations from itsmio nuclei were found to be more penetrating than could be explained by theory, and the qualities of ether radiations were less than those predicted by calculation. None of these anoaalies was enough to force radical mwvations of conception. Experimenter assumed that further research rnmld resolve these anomalies without th» wtwodnction of new fundamental idem. AAHWKMAL RADIOACTIVITY, Bat when early in 1932 J. Chadwick shewed that one of the anomalies was duo to the existence of a new sort of particle, the neutron, a new period m atomic research began. Within a few weeks Cockcroft and Walton were inspired to attempt and succeed in disintegrating atoms by electrical machinWithin a few months Anderson announced the discovery of the positron. Early this year the Curie-Joliot* (daughter and son-in-law of the late Mme. Curie) announced the discovery of artificial radioactivity. Shortly afterwards Cockcroft and his collaborators showed that artificial radioactivity could be produced by their machinery. Now Fermi announces the discovery of dozens of new radioactive atoms, and Williams advances evidence for the existence of still another particle, the negation. Since Chadwick’s discovery the universe has begun to swarm with new particles. Before it the theoreticians had monopolised the field for a decade. In 1931 the material universe appeared an a building made of two sorts of bricks, electrons and protons. The vision of this building js now transfigured into a structure of electrons, positrons, and neutrons, and, perhaps, of protons and negatrons. THE BASIS. The Ourie-Joliots discovered artificial radioactivity by bombarding substances such as aluminium with the alpha particles ejected from the natural radioactive substance, polonium. The aluminium atoms are transmuted into atoms with the same chemical properties as phosphorus atoms, but differ from them in being unstable. After an average life of a few minutes these radiophosphorus atoms disintegrate and enut positrons. Cockcroft has shown that radio-njtrogen can be prepared from carbon by bombarding it with protons. Crane and others have shown that similar results can be obtained by bombarding various atoms with dipions, or heavy hydrogen. In all of these methods charged particles are used as the projectiles. They are ineffective with heavy atoms such as those of gold, because the electric charge on a gold atomic nucleus is high and prevents the charged bombarding particle from approaching the nucleus closely. As a neutron has no charge it should not be prevented from entering heavy atomic nuclei. Proceeding on this consideration, Fermi has tried bombarding heavy atoms with neutrons, and has obtained results which seem to show the occurrence pf remarkable transmutations. In collaboration with F. Rasetti and O. D’Agostino he investigated with particular attention the bombardment of uranium and throium with neutrons. NEW TRANSFORMATIONS. He found that a complicated series of new transformations occurred. These seem to be due to the formation of five or more new sorts of radioactive atoms. One of these has an average life of about thirteen minutes. Chemical investigation shows that its chemical properties are different from those of uranium and several other atoms. It is improbable that this new atom obtained by bombarding uranium with neutrons is a radio-active form of any of the known atoms. Fermi suggests it may be atom No. 93, or possibly 94 or 95. Hitherto only 92 different chemical sorts of atoms have been known. It has been assumed that the heavier atoms 93, etc., must be unstable, and that if they ever existed on the earth they must have disintegrated long ago. If No. 93 could exist it should presumably be unstable and have chemical properties similar to those of manganese and rhenium. There is no obvious reason why No. 93 should be incapable of existing. Some theorists have offered arguments to show that the number of possible chemical atoms must be limited to about one hundred, but the soundness of these arguments is uncertain. Impurities present one of the great technical difficulties in experiments of the type made by Fermi. In the past results of a rather similar type have been found to be due to the disintegration of impurities in the uranium and not to the disintegration of the uranium atoms. Much more research will t»e necessary before the possible existence of element No. 93 becomes certain.