[gippgig]

A good article was just published evaluating possible ways to make new elements (Physical Review C 78 034610). The conclusion is that making 117 by the ²⁴⁹Bk(⁴⁸Ca,3-4n) reaction is easy, reaching 120 is possible, and a factor of ten improvement in equipment might reach 124. Compare with the other article I mentioned in the previous entry that predicted a steep drop in cross sections around 119!

[Dan1195]

Clearly improved equipment and detection capability, combined with fine tuning the reactions, will the important in producing new elements, but also producing higher quantities of already known isotopes. Good progress within the past few years in regards to the latter has been made, particularly with neutron deficient Sg & Bh isotopes. With hundreds to thousands of decays observed, the small EC/SF branches of these isotopes have been detected.


Also in Phys. Rev. C This month was a discussion on producing neutron deficient actinides, an area of the nuclear chart with very poor data, especially from Pu-Cf. There was also a announcement of the producton of ²⁴¹Fm at GSI (and a questioning of the 800 us half-life of ²⁴²Fm), Though I have yet to see the actual paper here.

[gippgig]

The paper on making ²⁴¹Fm at GSI is in (or will be in) The European Physical Journal A ("DOI 10.1140/epja/i2008-10608-4").
There is also a definite need to make improved targets such as ²¹⁰Pb, ²⁵⁰Cm (I've mentioned this one before & will continue to do so until someone takes it seriously), & ²⁵⁴Es (the old LEAP plan). Note that the Pb & Cm targets have long lives so once made they could be used over & over again.

[Mitch]

Getting EH&S to approve anything more active than nat U is a hassle. We recently got approval to use 242Pu as targets and ran it with a Mg beam.

[Dan1195]

The data on ^241-244Fm was finally put into the XUNDL database and have a couple observations:

1. The 0.8 ms half-life observed previously was likely ²⁴¹Fm

2. The SF half-life of ²⁴²Fm is likely between 500 ns-1 us, which is of course too short for for the detection system. I base this prediction on the decline of SF half-lives in adjacent Even-Odd Fm nuclei (²⁴¹Fm and  ²⁴³FM (9% SF branch)). The relation of SF half-lives Even-Odd and Even-Even Rf isotopes is also a helpful guide here. Both ²⁵³Rf and ²⁵⁵Rf have SF half-lives longer by a factor of 1,000 compared to ²⁵⁴Rf and ²⁵⁶Rf.

Fm-241 = 730 us
Fm-242 =
Fm-243 = 2.6 s
Fm-244 = 3.12 ms

Rf-253 = 11 ms     
Rf-254 = 23 us
Rf-255 = 3.2 s
Rf-256 = 6.4 ms

3. The non-observance of an alpha branch in ²⁴⁴Fm. Based on systematics the percent alpha is likely close to 1% or just beyond the limit of the sensitivity of the experiment. (The alpha half-life of ²⁴⁶Fm is 1.2 s),