2007-9-13

James Chadwick was born in Manchester the United Kingdom in October 1891, and graduated with remarkable records from the Physics College of Manchester University in 1911 and then he moved to be engaged in radioactivity in this university under the guidance of Professor Rutherford during 1911~1913 and conferred with master degree in Physics. In 1923, he was appointed as the Director Assistant of Cavendish Laboratory until 1935. During this period he discovered the neutron in 1932 in cooperation with Rutherford. For this discovery, he won the Nobel Prize in Physics in 1935.
 
In 1919, Rutherford discovered the proton by using ¦Á particle to bomb nitrogen atoms for releasing nitrogen nuclear. Later in 1920 in one of his lectures he talked, since the atom contains negative electron and positive proton, why should it no contain neutral "neutron"? At that moment, the neutron in his mind is the combination of electron and proton. In 1930, Germany physicists Bothe and Becker discovered with Geiger counter that metallic beryllium produced a kind of high-penetrability radiation when it was bombed by ¦Á particle; people at that time regarded that this radiation was a kind of high-energy and hard ¦Ã radial. In 1932, Mr/Ms. Joliot Curie repeated this experiment and were amazed to find that this kind of hare hard ¦Ã radial had an energy much greater than that of ¦Ã radial from a natural radioactive substance. There was another amazing discovery in this experiment that proton could be produced from paraffin wax by bombing it with such kind of radial. Mr/Ms. Joliot Curie called this phenomena as Compton effect. However, the bombed proton energy was as high as 5.7MeV, they could not explain this phenomena theoretically with Compton formula since this high energy would require a minimum 50MeV ¦Ã radial as the injected ¦Ã radial. Rutherford was delighted hearing of what James Chadwick told him about this, and Rutherford disagreed the explanation made by Mr/Ms. Joliot Curie. Quickly, James Chadwick repeated this experiment. By bombing beryllium with ¦Á particle to produce radial and using the produced radial to bomb hydrogen and nitrogen, he produced hydrogen nuclear and nitrogen nuclear. Based on this result, he concluded that this radial was absolutely not ¦Ã radial. Because ¦Ã radial had no momentum to produce proton from atom. He believed that this was reasonable only when this radial from beryllium was a kind of neutral particle with a mass similar to the proton.

Followed that, he measured the velocity of the produced hydrogen nuclear and nitrogen nuclear based on which he calculated the mass of this new particle. James Chadwick also tried other materials for this experiment and drew the same conclusions that this unknown particle had a mass similar to that of hydrogen nuclear. Since this kind of particle has no electric charge, therefore it is called neutron. This was proved by later more accurate measurement that the mass of neutron was very close to that of proton-only greater 1/1000 than the mass of proton. James Chadwick then concluded his discovery in his paper entitled ¡°The Existence of the Neutron¡± and published in the Royal Academy Journal. James Chadwick discovered the neutron by repeating the experiment done by Mr/Ms. Joliot Curie within a period no more than one month. Because he benefited from the work done by others, importantly he got this fruit because of his unconventional thinking and innovation as well as his breakthrough of the tradition.

Unfortunately, though Mr/Ms. Joliot Curie found the neutron, they failed to give an explanation to convince others and themselves and resulted them to miss the change of the discovery of the neutron.