Blurring the Boundaries of Existence
28 Mar 2014 04:57 PM
A
team of researchers led by the nuclear physics groups at the University of
Liverpool, STFC’s Daresbury Laboratory and the University of
Jyväskylä in Finland have discovered that nuclei can exist in special
states that blur the boundaries of existence. This research highlights how UK
technology and expertise is enabling research into the behaviour of isotopes
that are so very rare they might only exist momentarily during stellar
explosions. Until now, these could have only been predicted through theoretical
calculations; but the reality is proving to be very different to the
theory.
In
a paper published in Physical Review Letters, the
team, which was supported by STFC, report the experimental discovery of an
isomer of tantalum with a structure that allows it to live longer than expected
before decaying.
Jurogam
(Credit: University of
Jyväskylä)
The
research was carried out at the nuclear physics research facility at the
University of Jyväskylä in Finland, where some of the key technology,
including the highly powerful GREAT and JUROGAMspectrometers
were designed and developed by STFC’s Nuclear Physics
Group and UK Universities, including Liverpool.
Identifying the full extent of the nuclear landscape
– essentially how many isotopes exist – is a long-standing issue of
fundamental importance for nuclear physics. Beyond the stable nuclei that we
find on Earth, there are many unstable nuclei that are formed in stellar events
such as supernovae, but which are short-lived. There is a limit to how many
protons and neutrons a nucleus can hold – too many and the excess
literally ‘pop out’. These limits are known as the proton and
neutron ‘drip lines’.
The
University of Liverpool’s Professor Robert Page, who led the research,
said: “We usually think of nuclear ground states as being the most
stable, but these results show that certain excited states have enhanced
stability and could extend the range of observable nuclei far beyond the drip
lines.”
Although these drip lines can be calculated
theoretically, experimental results rarely agree. Finding them experimentally
is a difficult prospect, and the research outlined in this paper was only made
possible by instrumentation designed and realised in the UK, and is now running
successfully in Finland.
Professor John Simpson, Head of STFC’s Nuclear
Physics Group, said: “Nuclear physicists look to create and study the
very rarest isotopes predicted to exist. It is really exciting to see
technology developed by the Nuclear Physics Group at STFC and UK Universities
contribute to this research that challenges theories that, until now, we have
only been able to predict. These scientific advances that are now emerging are
the result of years of innovative technical development and investment by the
UK and a strong and fruitful collaboration with the University of Jyväskylä".