Time resolved on-line nuclear orientation (TR-OLNO)

Abstract

Conventional on-line nuclear orientation (OLNO) involves continuous implantation of unpolarised nuclei which are cooled to milli-Kelvin temperatures by nuclear spin lattice relaxation. Anisotropy of radiation from the cold, polarised nuclei is analysed to yield nuclear moments and decay properties. Incomplete relaxation prior to decay complicates analysis and, as half-lives shorten on moving further from stability, places an ultimate limit on the range of nuclei which can be studied by OLNO. This paper introduces a new method, time resolved on-line nuclear orientation (TR-OLNO) in which the implanted beam is pulsed and study is made of the nuclear relaxation itself to yield nuclear g-factors. Decay scheme parameters can also be extracted when the relaxation is observed. This method has its optimum application as half-life and relaxation time become comparable, thus extending the range of the OLNO technique. The basic principles of the new method are introduced and its application to the study of decay chains of implanted even- and odd- A nuclei is discussed. The ability to deal with “inherited” orientation in a decay sequence is emphasised. Examples are given of existing TR-OLNO studies of light Au isotopes by the NICOLE Collaboration.