Francis William Aston
"There
is scarcely a research in nuclear physics which does not use his work,
directly or indirectly, and usually many times over."
- G.P. Thomson
 On
1st September 1877 Francis William Aston was born at Harborne, a few
miles from Birmingham. He was the third child in a family of seven,
and enjoyed playing with mechanical toys in his youth.
Aston was first educated at Harborne Vicarage School,
but began to study science at Malvern College, where he demonstrated
his ability in chemistry, physics and mathematics. Aston was at Malvern
for two years before entering Mason College, Birmingham, in 1893.
At Mason College, Aston was taught chemistry by Tilden
and Frankland, and physics by Poynting. In 1898 he was awarded the Forster
Scholarship and worked in collaboration with Frankland to publish his
first paper in 1901.
For financial reasons Aston left the college and began
working as a fermentation chemist at a brewery in Wolverhampton, where
he stayed for three years. In 1903 Aston decided to return to the college,
which had now become the University of Birmingham. With Röntgen's
recent discovery of X-rays, Aston's interests had turned to physics,
and he began studying the properties of gas discharges.
In 1908 Aston's father died, leaving Aston enough money
to travel around the world. The following year Professor J.J. Thomson
invited Aston to move to the Cavendish Laboratory and work as Thomson's
assistant. Aston had been recommended to Thomson by his former teacher
Poynting, and was happy to accept the Cambridge post which would leave
him more time for research. Since his discovery of the electron Thomson
had been analysing positive rays, and had developed a method of measuring
atomic weights by using combinations of magnetics and electric fields
to produce curves on a photographic plate. Aston helped to further refine
these experiments.
Thomson and Aston found an unexpected effect when they
investigated the element neon. Instead of showing only one curve on
the photograph, it showed two, suggesting that the element was made
up of two different types of atoms which were chemically identical but
of different mass, named isotopes. This interested Aston, and he devoted
the rest of his career to developing the mass spectrograph capable of
accurately measuring these chemical isotopes.
Aston's work was interrupted by the First World War,
when he worked as a chemist at Farnborough in the Royal Aircraft Factory,
investigating the canvas used to cover aeroplanes. In 1914 he crashed
in an experimental aeroplane, but escaped unhurt. He lived in a civilian
mess with other scientists including Frederick Lindemann and J.J.'s
son George Thomson. Lindemann was sceptical of Aston's isotope hypothesis,
but Aston's opinion wouldn't be swayed and he enjoyed this opportunity
to discuss his ideas with close friends.
After the war Aston returned to the problem of the neon
isotopes, and constructed his first mass spectrograph. The apparatus
clearly showed the two types of neon, and also showed isotopes for chlorine
and many other elements. It was an almost immediate success, and Aston
received quick acclaim. He was elected a fellow of Trinity College,
Cambridge, in 1920, and lived there for the rest of his life. The following
year he was elected to the Royal Society, and in 1922 he won the Nobel
Prize for Chemistry in 1922.
Aston continued to improve his mass spectrograph, and
succeeded in analysing most of the chemical elements. In all but a few
cases he made the first isotopic analysis. His first spectrograph had
established the 'whole number rule', that the masses of all elements
except hydrogen are a whole number of atomic mass units. The improved
accuracy of his second spectrographs measured the differences from this
rule, which gave details of the forces holding atoms together. Aston's
third and final mass spectrograph had an accuracy of 1 in 100,000.
In later years other scientists began building mass
spectrographs, but there 'are few instances in modern science in which
the first discoverer of a major field of research has had it his own
way for such a long time'. Modern spectrographs have an accuracy of
about 1 in a billion.
Aston had many interests outside his work. He enjoyed
sport, especially winter sports, and was an enthusiastic skier and rock
climber. He would take annual visits to Switzerland and Norway for long
skiing exhibitions, until he began to suffer from a heart condition
in late 1934. He played tennis at tournament class, and golf in a famous
foursome with the other Cavendish physicists Ernest Rutherford, Ralph
Fowler and G.I. Taylor.
Aston combined his love of sport with a love of travelling.
He once cycled two hundred miles in a single day. He considered 'surf-riding',
which he learnt in Honolulu, to by the finest sport in the world. He
would combine this love of travelling with his scientific work, and
would often go on expeditions to see eclipses around the world. He was
also musical and could play the cello, piano or violin.
Aston enjoyed life and was interested in the world.
He was precise and conservative, but could accept new ideas with great
relish. He gave good occasional lectures but didn't teach, as it took
too much time away from his research.
Aston published many papers and wrote his book 'Isotopes'
in 1922, later reprinted as 'Mass Spectra and Isotopes'. As well as
his Nobel prize he won the Hughes and the Royal Medals from the Royal
Society, and was given honorary degrees by Birmingham and Dublin.
Aston never married and lived in Trinity College for
thirty-five years, until he died on 20th November 1945.
Read a biography of Aston at the Nobel e-museum:
www.nobel.se/chemistry/laureates/1922/aston-bio.html
Reference:
'Dr. Francis William Aston, F.R.S.', G.P. Thomson, Nature 157,
290 (1946)
'Francis Aston and the mass spectrograph', Gordon Squires, Dalton Transactions
23, 3893 (1998)
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