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A steady-state theory of the discharge column is derived which is applicable in the pressure range where the ion mean free path is neither much greater than nor much less than the column radius, and which goes over in the low- and high-pressure limits to the free-fall and ambipolar diffusion theories, respectively. Solutions for planar and cylindrical geometry are given for the density and potential profiles. The plasma-sheath boundary is discussed and the sheath potential drop is estimated. The theory is shown to agree well with measurements in mercury discharges over the pressure range 1–20 μ Hg.

Very neutron deficient isotopes in the Hf-Re region were produced by bombarding targets of 1~176 nat'l~176 and l~ with 5SNi accelerated by the linear accelerator UNILAC at GSI. After separation from the projectile beam by the velocity filter SHIP, the fusion products were implanted with their full recoil energy into a silicon surface barrier detector. The subsequent alpha decay of the implanted ions was measured with the same detector. In some of the experiments the evaporation residues were implanted into a position sensitive silicon surface barrier detector. With a newly developed position and time correlation technique parent daughter relationships, half lives, and ~ branching ratios of a large number of isotopes could be determined. In the investigated reactions the eleven new isotopes 161-164Re, 16~157-161Ta, and 156Hf could be identified. The measured Q~ values, half lives, and ~ branching ratios are discussed. Two new high energy c~ transitions of (7,408+10) keV and (7,804_+ 15) keV were also found with half lives of 2.7 ms and 0.52 ms, respectively. A tentative mass and atomic number assignment gives A = 153-156 and Z =70-72. The energies of the excited isomeric states are between 2 MeV and 3 MeV. From the systematics of alpha ground state transitions in even nuclei a hindrance of l0 s can be deduced for both transitions, possibly indicating orbital angular momenta on the order of 10h for the alpha emitting states. The isomers are proposed to belong to shell model isomers beyond la6Gd.

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