Oh Vienna

 I'm making my first trip to the International Atomic Energy Agency (IAEA), my first trip to Vienna, and my first trip to Austria.  I'm attending the CNR'24 (Compound Nuclear Reaction) conference on the IAEA premises which is part of the UN buildings in Vienna.  It's a pretty amazing and iconic venue, though having to go through airport-type security to get in is a slight pain.  

The compound nucleus is the name given to the state of a reacting nucleus that occurs typically after the capture of a neutron or a heavier ion to form a highly excited state which is relatively long-lived and which quickly redistributes the nucleons from the impinging system in such a way that details of the initial reaction are 'forgotten' by the system.  The picture is sometimes given of marbles sitting in shallow bowl, or depression, with another marble coming in from outside with enough energy to pass through the depression, except that it knocks into the marbles already in there, shares its kinetic energy with them so that it gets captured and no individual marble has enough energy to leave.  In principle there is enough energy there so that after enough collisions one of the marbles can be kicked out, and eventually, in a frictionless ideal situation, such an even will happen.  In real compound nuclei sometimes this does really happen, and very narrow neutron resonances can be found which correspond to very long-lived states.  

The term "compound nucleus" was coined by Niels Bohr in the early days of nuclear physics when trying to understand some of the first-observed phenomena in nuclei and its impressive that the ideas were sufficiently correct that they have survived today.  Some of the calculations I am interested in, such as those creating giant resonances, causing fission, or during fusion to make superheavy elements, have this compound nuclear state as an intermediate nucleus.  I've never really thought about the properties of this compound nucleus in detail, but having talked to one of the conference co-organisers earlier in the year, I realised that I would find the conference pretty interesting, and so it has been.

I've been to many conferences over the years, and one of the things I've seen is the people who enjoy meeting up with colleagues who they have seen throughout their careers at different occasions and throguh such meetings form friendships which endure over the years.  I've somewhat felt that that's part of the conference experience that I've missed out on, partly through a natural diffidence that has perhaps affected my ability to form friendships outside of my professional life as much as in it, but here I have indeed bumped into a few people who I have really been able to catch up with and talk about the last time we have seen each other, mixing up asking about latest work results alongside how they are doing and how life has changed since seeing each other last.  It's a nice part of the conference experience.

Here's my obligatory blogpost picture - me standing in the plaza area of the UN complex