Research Highlights

• α-decay of ¹⁰⁹I

Phys. Rev. Lett. 98, 212501 (2007)

We have observed for the first time α-decay from the proton emitting nucleus ¹⁰⁹I. Occurring just 3 times in 20,000, the measurement of this decay branch has enabled limits to be placed on the production of astrophysically significant nuclei. These nuclei, important in the termination of the rp-process, help us understand the nuclear reactions, and thus the light profiles, of dying stars such as Type I X-ray bursts. Our publication in PRL was selected by the editors as one of their suggestions for reading across all fields.

Illustration of a neutron star X-ray burst.

Credit: NASA/Dana Berr

• Discovery of superallowed α-decay of ¹⁰⁵Te

Phys. Rev. Lett. 97, 082501 (2006)

Classically, α decay occurs through the preformation of an α particle in the nucleus and its subsequent tunneling through Coulomb and centrifugal barriers. Close to the N = Z line, above ¹⁰⁰Sn, protons and neutrons are expected to occupy identical orbitals. This may result in an enhancement of the preformation probability of an α-particle within the nucleus and the onset of so-called superallowed α-decay. Two new α emitters ¹⁰⁹Xe and ¹⁰⁵Te were identified through the observation of the ¹⁰⁹Xe → ¹⁰⁵Te → ¹⁰¹Sn α-decay chain.  The observation of the subsequent decay of ¹⁰⁵Te marks the discovery of the lightest known α-decaying nucleus and is consistent with a superallowed character.

• Two proton Correlations in the decay of ⁴⁵Fe

Phys. Rev. Lett. 99, 192501 (2007)

The decay spectroscopy group have, in a collaboration led by scientists from the Institute of Experimental Physics (IEP), Warsaw University (Poland), performed an experiment resulting in direct and unambiguous proof of the new phenomena of ground-state 2-proton radioactivity. This new form of radioactive decay has been proved using a novel imaging technique of nuclear decays. To achieve this our colleagues developed a new type of detector - the Optical Time Projection Chamber (OTPC) which records images of tracks of charged particles.[more]

CCD photo of ⁴⁵Fe after decaying via 2 protons

• First observation of β-delayed 3 proton emission in ⁴⁵Fe

Phys. Rev. C. 76 041304(R) (2007)

A characteristic feature of the β-decay very neutron deficient nuclei is the possibility of proton emission from highly excited states populated in the daughter nucleus. This phenomenon becomes particularly important when the proton drip-line is approached. Due to increasing decay energy and decreasing proton separation energy, many decay channels open, including multiparticle emission.  Using the OTPC direct and unambiguous pictures demonstrate β-3p emission from ⁴⁵Fe.

CCD photo of β-delayed 3p emission from ⁴⁵Fe.