E. Coenen

Low-lying Jπ=0+ states in 190,192Pb populated in the α-decay of 194,196Po

Abstract Further experimental evidence for a low-lying J π =0 + excited state in the neutron-deficient lead isotopes is obtained. This was done via a study of the α-decay of mass-separated 194,196 Po. The excited 0 + state in 192 Pb at 769 keV is confirmed and an excited 0 + state in 190 Pb at 669 keV has been found.

LIGISOL: The Leuven ion guide isotope separator on-line

Abstract The development of a new ion-guide facility for mass separation operating on-line with a heavy-ion accelerator is described. Different aspects related to the ionisation principle for reaction products with high recoil energies are discussed. It is proven that this ion-guide technique can be developed further to become one of the most general separation techniques, independent from physical (half-life, recoil energy,…) or chemical (refractoriness,…) characteristics.

Intruder states in odd-odd Tl nuclei: The completion of a unique set of intruder systematics

Abstract The α-decay of mass-separated Bi isotopes is studied to characterize shell-model intruder states in odd-odd Tl nuclei. By studying both experimentally and theoretically the members of the π 1 h 9 2 intruder -ν li 13 2 multiplet, the position of the intruder-based multiplet could be extracted. The scaling of intruder-state energies is discussed.

β+/electron-capture decay of192,194,196,198,200Bi: Experimental evidence for low lying0+states

Levels in the /sup 192, 194, 196, 198, 200/Pb isotopes were studied via the ..beta../sup +//electron-capture decay of mass separated Bi isotopes. Multiscaled spectra of ..gamma.. rays, x rays, and conversion electrons, and ..gamma..-..gamma.. and ..gamma..-e/sup -/ coincidences were measured. The existence of 0/sup +/ states in the /sup 192-200/Pb nuclei is shown and evidence for the beginning of a collective band built on top of the 0/sub 2//sup +/ states is seen in /sup 192, 194, 196/Pb. A discussion in terms of characteristic properties of intruder states in the even-even nuclei and in terms of a one-broken-neutron-pair formalism is given. This shows clearly the presence of both neutron and proton (..pi..(2p-2h)) based states in the semimagic Pb nuclei at low excitation energy.

Decay study of103In and105In

An extensive decay scheme of105In, involving nearly 140 transitions and 35 levels in105Cd, as well as a tentative decay scheme of103In are proposed. A number of previous inconsistencies between earlier decay scheme work of105In and in-beam work on105Cd are removed. It is shown that the simple particle plus core treatment does not suffice to describe all states. A cluster plus core model seems to be an indispensable completion of this model, especially for the description of the low lying low spin states. Also the conversion coefficients of the internal transitions in105In and107In are measured. The results are well accounted for by the Moszkowski single-proton transition probabilities.

First identification of γ-rays in the β+/EC decay of 104,105Sn

The beta +/EC decay of mass-separated 104Sn and 105Sn isotopes was studied by X-ray and gamma -ray singles, as well as by X- gamma and gamma - gamma coincidences. Sources were produced in the reactions 92Mo (20Ne,ypxn). The nucleus 50104Sn with T12/=23+or-2 s was identified. A partial decay scheme of 105Sn is proposed.

Decay of mass-separated 3.0 min 195gBi to levels in 195Pb and shape coexistence in the neutron-deficient odd-mass Pb isotopes

Abstract The radioactive decay of mass-separated 3.0 m 195g Bi to 195 Pb has been studied with the UNISOR and LISOL facilities. Time-sequenced spectra of γ-rays, X-rays, and conversion electrons have been obtained, together with γγt, γXt, eγt, and eXt coincidence data. From this information, a decay scheme has been constructed consisting of 23 excited states and 34 transitions in 195 Pb. Transitions with E0 multipole admixtures, indicative of shape coexistence, have been found to de-excite positive-parity levels at 1093, 1329, and 1380 keV. The beta-decay energy of the 195 Bi ground state is deduced to be Q EC = 4800 −550 +600 keV based on the measurement of γ-ray-gated K / β + ratios. The excitation energy of the i 13 2 isomer in 195 Pb has been determined to be 203±4 keV from the α-decays of 199m,g Po.

First identification of a 1/2+ intruder state in the197At isotope

The α-decay study of mass-separated nuclei in the region around Z=82 provides a strong spectroscopic tool to investigate intruder states. In this note, this method is applied to the197At isotope.

Decay study of neutron-deficient101In

The very neutron-deficient nucleus101In has been identified for the first time by studying the β-delayed γ rays of on-line mass-separated samples. The deduced half life is 16(3)s. This study assigns a hitherto unplacedγ ray cascade of a recently published in-beam study to101Cd.

Shape coexistence in the region around Z=82

A survey of the experimental work done at the Leuven Isotope Separator on Line Facility on intruder‐state systematics and shape coexistence in the region around Z=82 is given. The excitation energy of the intruder based states in the odd Bi, odd Tl, odd‐odd Tl and even‐even Pb nuclei show, in function of the neutron number, a remarkable coinciding behavior. This indicates the general applicability of the scaling law near the Z=82 proton closed shell.