piercebeatz said:
Hello,
Is there a quantum mechanical reason why elements 119+ might not exist? i.e. would the crazy orbitals associated with these elements violate the laws of physics in any way?
Not really! You've got to distinguish between "atom" and "nucleus" here - there is reason to suspect you will begin to not be able to make neutral atoms from relativistic quantum mechanics, but careful analysis suggests not.
But, what we actually care about is whether we can produce nuclei with Z>119. And there is no law that says we won't be able to - I work in a research group that spends a lot of time examining the reactions that you can use to produce Z>119 (but I work on the other end of the nuclear chart). In fact, it is only thanks to quantum mechanical models that superheavy elements can exist - you need, at the very least, the shell model.
Up until now, we've used reactions of 48Ca (a doubly magic nucleus) on 248Cm, 249Cf or 249Bk to produce Z =116 - 118 respectively. However, this won't work for Z = 119. The most popular candidate for 119 is 50Ti on 249Bk. But it's not a simple matter to decide which two nuclei to smash together!
The trouble is, is that we're very good at producing compound nuclei that are a little proton rich, but the models tell us that any island of stability will be on the neutron rich side of the chart - so we need to add more neutrons into the system. Unfortunately, it's not as simple as just chucking in more neutrons - nuclear structure considerations need to be taken into account, which change the candidate reactions.
The other difficulty is that the odds of making these nuclei are
incredibly tiny. You need the best part of a year of beam-time to produce maybe 6 of your candidate nuclei, which is why there are only 3 places in the world that can produce new elements (LBNL, Dubna, GSI). Further, isotopes like 48Ca, Bk, and Cf are incredibly hard to produce, so there is only one or two places you can get the ingredients! (Oak Ridge, USA and Dimitrovgrad, Russia).
Another(!) difficulty is that you don't discover these elements by directly detecting the new nucleus. What you do is wait for them to decay via alpha-emission to a known nucleus, which will then decay via alpha-emission to another known nucleus, and so on and so on, so you've got to pick out the signals of these decays in amongst all of the other signals that you're getting on the detectors from the beam - one obvious choice would be to pulse the beam, and only look for the decays when the beam is "off", which is what happens, but these superheavies are actually relatively long lived - on the order of microseconds - so that becomes a big pain. Digital electronics have been a great help here, as are sophisticated magnetic filters.
Phew. And as to whether you can predict the half-lives? Hah! The trouble is that nuclear models are pretty awful at predicting this kind of thing away from stability. We don't actually know for sure where we expect to find the next shell closure (magic nucleus). If you ask 4 different theorists, you'll get 4 different answers. Possibly more if you put them in a room together and argue.
