Wednesday, 20 June 2012

The Nature of Tin-100

Some large fraction of experimental work in nuclear physics concerns exploring the boundaries of what nuclei exist in nature and how they behave.  Nature allows nuclei - made of protons and neutrons - in certain combinations only.  Broadly speaking, the number of protons and neutrons should be similar, and not too large.  The conditions are set by the fact that protons like sticking to neutrons and vice versa, but not so much to each other, but as long as there are roughly equal amounts then it's okay, and that protons, being electrically positively charged, don't like to congregate together in large numbers.  This second effect means that when you start getting to the heavier elements (with >20 protons, say) then the proton to neutron ratio favours neutrons.

One of the most "exotic" nuclei with the same number of protons and neutrons yet observed in the laboratory is Tin-100, with 50 protons and 50 neutrons.  This is a particularly special case, since 50 is a so-called magic number in nuclei, which means that having 50 particles of one type is a particularly stable configuration.  The fact that it is heavy and does not have the excess of neutrons to balance the repulsive electric force means that it is nevertheless a bit on the unstable side.

Still, having these magic numbers makes it important to study, as the structure should be particularly clean and easy to understand from a theoretical point of view, which is why my colleagues have just published this article in Nature describing some of its properties.  Particularly they have looked at the beta-decay, which gives a measure of the structure of the nucleus as a proton decays into a neutron to turn it in to the neighbouring nucleus Indium-100. 

Good job Surrey colleagues, and I'm sure our REF coordinator will be pleased, too.

Tuesday, 19 June 2012

End of the year

It's that time of year when semester has just finished.  The undergraduate students have left, and we have had our first examination board meeting today, with the external coming along later in the week for a second meeting.  It's nice to see the results of the hard work of most of the students, and I'll look forward to the graduation ceremony next month, where I get to dress up in academic dress and see the students do the same as they are formally awarded their degrees.

So now I have three months ahead of me with little UG teaching-related activity.  Except that I'll be teaching a new course called "Advanced Computational Techniques" in October, so need to get that in to shape.  First stop, though, is conference in Bulgaria.  Hopefully my white linen suit from an online made-to-measure tailor will arrive in time...

Friday, 1 June 2012

C. S. Wu

Having noticed in my last post, somewhat after the fact, that it would have been the 90th birthday of Andrei Sakharov recently, I notice that my SEPNet colleague, Karen Masters, has just blogged about the 100th anniversary of the birth of another giant of nuclear physics, C S Wu.  Read her post here.