Confirming stable new elements?

[Loren Booda]

Trans-uranium element production is more often confirmed from decay products. But would such a new atom be overlooked if stable? Recently, element 118 occurred in one out of 10¹⁹ collisions, and was most readily detected by its signature radiation.

 

[mathman]

Your question is academic in that elements with atomic no. >82 have no stable isotopes (Bi was recently discovered to be radioactive).

 

[Loren Booda]

How many elements have, or beyond what weight have they, been observed by methods other than decay (by eyesight, say)? Have there not been rumors of comparatively stable trans-uranium elements?

 

[humanino]

Your question is academic in that elements with atomic no. >82 have no stable isotopes (Bi was recently discovered to be radioactive).

I may misunderstand your objection, but you may also be unaware of the timescales involved. Take 1 fm as a typical nuclear size. Take the speed of light as a typical velocity (we are only interested in the odrer of scales involved). You will find that, the time it takes for a nucleon to go from on side of the nucleus to the other is of the order $$10^{-24}$$ s. Here we are talking about nuclei with halflives above 1 ms. This is a huge time at the nuclear scale. Besides, it could very well be that, in the island of stability, there are elements with halflives of the order of days.

So I find the question is not academic at all. The key is that, there are several facilities around the world and several experiments at each facility. The different experiments are dedicated to look at a given scale in lifetime. In particular, very stable elements are easy to detect by "eyesight", just by using Wien filters which, for a given energy, select the ratio of the mass to the charge. Combined with regular dipoles, you can get rid of huge backgrounds and keep only the elements you search for.

Even though I am not an expert in superheavy ions research, I am pretty certain that too much stability is not an issue.