Measurement of half lives of exotic nuclei of P, S and Cl*

To understand the universe better, it is important to understand the behavior of nuclei that are far away from the line of stability. It can help us understand how the nuclei behaved billions of years ago before settling to those presently stable elements that we now see. This paper reports on the measurement of half lives of four such unstable neutron rich nuclei, namely  42P, 44S, 43S and 45Cl. These isotopes eventually  beta decay to mostly excited states in the daughter nuclei which decay by  gamma rays that are detected by  gamma ray detectors and provide information about the internal structures of both the parent and daughter nuclei. The experimental work for this paper was performed at National Superconducting Cyclotron Laboratory (now Facility of Radioactive Ion beam) at Michigan State University using the Beta Counting Station along with an array of sixteen high purity Germanium detectors.  

The implant (nuclei of interest) and ensuing beta particles were both detected in a pixelated double sided Si strip detector and the time difference between them was used to generate a decay curve for that implant. As these nuclei are quite far away from stability, even the daughter nucleus is unstable and undergoes further decay before it reaches a stable nuclear configuration. The task of finding the half lives which are of the order of milliseconds involves fitting the decay curves with the full decay chain following the Bateman equations. Many a times the states fed in the beta decay are above the neutron separation leading to neutron decay which also has to be taken into account. Further confirmation of the half life can be obtained by following characteristic gamma rays in the daughter nuclei. 

The results from this experiment provide us new information about these exotic nuclei and details will be presented.