Low-lying isomeric states in Ga80 from the β− decay of Zn

Abstract

A new level scheme of 80 Ga has been determined. This nucleus was populated following the β − decay of 80 Zn at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s β − -decaying 6 − isomer is the ground state of 80 Ga and the 1.3-s β − -decaying 3 − isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions.

Collinear laser spectroscopy at ISOLDE: new methods and highlights

“…Only at 81 Ga, at N=50, does the ground state actually become 5/2 − . Also, a new isomeric state was observed in 80 Ga [66] and its beta-decay properties were recently measured at ISOLDE [78]. Laser spectroscopy was also well-placed to confirm the existence of and firmly assign spins to long-lived isomeric states in the Zn isotopes.…”

“…Highresolution experiments on Cu isotopes using optical detection could be performed up to 75 Cu, establishing experimentally the spin inversion [49]. Low-resolution in-source resonance ionisation spectroscopy proposed a ground state spin/parity 5/2 − for 77 Cu as well [76], and this was recently confirmed by high-resolution studies up to 78 Cu, using the high-resolution CRIS technique (see section 3.3 for details on the method). Data are currently being analysed and details on spins, radii and moments will be extracted [77].…”

“…The data are being analysed and example spectra for 75,77 Cu are shown in figure 8. For copper the sensitivity of the CRIS method has been pushed now to a few 10 ions s −1 , allowing the study of 78 Cu. Further improvements should be possible in ionisation efficiency as well as background reduction, giving hope for a study of 79 Cu with less than 10 ions s −1 .…”

Fast-timing spectroscopy at ISOLDE

“…The time resolution given as the full width at half maximum (FWHM) for an individual cylindrical crystal 1 inch in height and 1 inch in diameter has been measured by our collaboration to be below 100 ps [12] for 60 Co peak-to-peak coincidences. This translates in a coincidence resolution time for a pair of similar crystals at the same energies of the order of 140 ps, thus providing very competitive results compared to BaF 2 .…”

“…The energy resolution for the 661.7 keV 137 Cs line is 9.0% for the best crystals and about 10.0% for most of them. In spite of the steady development of inorganic scintillators for γ detection, BaF 2 is still the fastest commercially produced crystal with time resolution of ∼80 ps FWHM for small ∼1-2 cm 3 crystals [9] and 150 ps FWHM for crystals of our Studsvik design at 60 Co energies.…”