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A chemically selective laser ion source has been used in a β-decay study of heavy Ag isotopes into even-even Cd nuclides. Gamma-spectroscopic techniques in time-resolving event-by-event and multiscaling modes have permitted the identification of the first 2+ and 4+ levels in 126Cd78, 128Cd80, and tentatively the 2+ state in 130Cd82. From a comparison of these new states in 48Cd with the E(2+) and E(4+)/E(2+) level systematics of 46Pd and 52Te isotopes and several recent model predictions, possible evidence for a weakening of the spherical N = 82 neutron-shell below double-magic 132Sn is obtained.

In order to improve the crystallization of APCVD silicon on amorphous substrates we have investigated different techniques to grow films with sufficient average grain size. An experimental study of the influence of substrate surface topology on nucleation and grain size of APCVD grown silicon is reported here. Oxidized silicon wafers with a striation pattern and pyramidal structure are used as substrates for deposition. The size of the striation pattern varies from 8 to 128 μm in period and from 40 nm to 36 μm in height. The pyramids and inverted pyramids (2-40 μm high) have been made using selective etching of (100) oriented wafers. A 20-50 μm thick silicon film has been deposited on all substrate types at high temperature (1100-1200°C) and SiH 2 Cl 2 partial pressure of 500 Pa. The structure of the deposited film strongly depends on the surface topology. To study the mechanism of this effect we have determined the nucleation densities on textured surfaces for a deposition time of 2 s. A value of 6-10 μm -2 was found. Although the free-energy change is lowered at the edges (E.I. Givargizov, Oriented Crystallization on Amorphous Substrates, Plenum, New York, 1991) there was no significant increase of nucleation density in these areas. Thus the effect observed is supposed to occur due to the change of geometry at competing grain growth. The described effect seems to be applicable to grow silicon films appropriate for solar cell production.

The use of chemically selective laser ionization combined with beta-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms Mn-61 up through 14-ms Mn-69. The measured half-lives are found to be significantly longer near N=40 than the values calculated with a QRPA shell model using ground-state deformations from the FRDM and ETFSI models. Gamma-ray singles and coincidence spectroscopy has been performed for Mn-64 and Mn-66 decays to levels of Fe-64 and Fe-66, revealing a significant drop in the energy of the first 2+ state in these nuclides that suggests an unanticipated increase in collectivity near N=40., Latex-file with 4 figures, 5 pages, Phys. Rev. Lett., in print

We have developed a chemically selective laser ion source at the CERN-ISOLDE facility in order to study neutron-rich Ag nuclides. A pulsed laser system with high repetition rate has been used based on high-power coppe-vapour pump lasers and dye lasers. With this source significant reductions of the isobaric background has been achieved.

To explore the nucleosynthesis of heavy elements in the rapid neutron-capture process, investigations on short- lived, very neutron-rich Cd isotopes are planned that require pure samples. These will be produced at the CERN-ISOLDE on-line mass separator in combination with a chemically se- lective laser ion source. The excitation scheme for resonance ionization of Cd was tested in Mainz with a copper-vapor- pumped dye laser system. Due to the high ionization potential of Cd, frequency tripling was required for the first excita- tion step.1D 228: 8n m/. Laser light with an average power of 2m Wwas obtained after frequency tripling and was suc- cessfully used for RIS test measurements on cadmium with a time-of-flight mass spectrometer. The eight stable Cd iso- topes could be identified unambiguously.

The use of chemically selective laser ionization combined with beta-delayed neutron counting at ISOLDE has permitted identification and half-life measurements for 61Mn up through 69Mn. The 14(4)-ms half life for 69Mn is one of the shortest determined for any nuclide beyond the sd shell. Gamma-ray singles and coincidence spectra have been determined for the decays of 64,66Mn to levels of 64,66Fe, revealing strong deformation and vanishing of the N=40 subshell in the Fe isotopes.

In a recent experiment at CERN/ISOLDE, we have used laser isotope separation to isolate heavy Ag nuclides including the N=82 r-process “waiting-point” isotope 129Ag. A half-life of 46(+5/−9) ms for the πg9/2 ground-state decay of 129Ag could be determined using beta-delayed neutron counting. In the case of 126Ag and 128Ag decays, γ-spectroscopic techniques with time resolving multi-channel-analysers were used to identify the 2+ and 4+ levels in 126Cd and 128Cd, respectively. The hyperfine splitting of the atomic transition in Ag which is used for laser ionization has made possible an isomer selection through which the β- and γ-decay of the high-spin isomer of 122Ag were observed while suppressing the ionization of the low-spin isomer.

New levels are reported for 124,126Cd populated in the decay of 124,126Ag isomers, respectively. In addition, new data from direct population of levels in 124Cd from alpha-induced fission of 238U are reported, along with new shell-model calculations for 126Cd.