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The masses of ^{246}Es, ^{251}Fm, and the transfermium nuclei ^{249-252}Md and ^{254}No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed N=152 neutron shell closure, have been directly measured using a multireflection time-of-flight mass spectrograph. The masses of ^{246}Es and ^{249,250,252}Md were measured for the first time. Using the masses of ^{249,250}Md as anchor points for α decay chains, the masses of heavier nuclei, up to ^{261}Bh and ^{266}Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter δ_{2n} derived from three isotopic masses was updated with the new masses and corroborates the existence of the deformed N=152 neutron shell closure for Md and Lr.

The hyperfine splittings of ground state Be+11 have been measured precisely by laser-microwave double resonance spectroscopy for trapped and laser cooled beryllium ions. The ions were produced at relativistic energies and subsequently slowed down and trapped at mK temperatures. The magnetic hyperfine structure constant of Be+11 was determined to be A11=-2677.302 988(72) MHz from the measurements of the mF-mF'=0-0 field independent transition. This measurement provides essential data for the study of the distribution of the halo neutron in the single neutron halo nucleus Be11 through the Bohr-Weisskopf effect.

High-precision mass measurements of proton-rich isotopes in the range of 60{le}Z{le}84 were performed using the novel technique of Schottky spectrometry. Projectile fragments produced by {sup 209}Bi ions at 930{ital A} MeV were separated with the magnetic spectrometer FRS and stored and cooled in the experimental storage ring (ESR). A typical mass resolving power of 350000 and a precision of 100keV were achieved in the region A{approx}200 . Masses of members of {alpha} chains linked by precise Q{sub {alpha}} values but not yet connected to the known masses were determined. In this way it is concluded that {sup 201}Fr and {sup 197}At are proton unbound. {copyright} {ital 1997} {ital The American Physical Society}

The ground state hyperfine splitting of $^{7}\mathrm{Be}^{+}$ has been measured by laser-microwave double-resonance spectroscopy in the online rf trap of RIKEN's slow RI-beam facility. Be ions produced by projectile fragmentation of $^{13}\mathrm{C}$ at $\ensuremath{\approx}1\text{ }\text{ }\mathrm{GeV}$ were thermalized in a rf ion guide gas cell and subsequently laser cooled in the ion trap to $\ensuremath{\approx}1\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$. This ${10}^{15}$-fold reduction of the kinetic energy allows precision spectroscopy of these ions. A magnetic hfs constant of $A=\ensuremath{-}742.772\text{ }28(43)\text{ }\text{ }\mathrm{MHz}$ was measured for $^{7}\mathrm{Be}^{+}$, from which a nuclear magnetic moment of ${\ensuremath{\mu}}_{I}=\ensuremath{-}1.399\text{ }28(2){\ensuremath{\mu}}_{N}$ was deduced.

Secondary beams from fragmentation of $^{58}\mathrm{Ni}$ have been produced with energies of $(200\ensuremath{-}220)A$ MeV, separated with a fragment separator and injected into a storage-cooler ring for half-life measurements. The relative momentum spread $\frac{\ensuremath{\Delta}p}{p}\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ (FWHM) which we achieved allowed us to resolve the ground and isomeric states of cooled $^{52}\mathrm{Mn}$ and $^{53}\mathrm{Fe}$ nuclei in the measured mass spectra. The circulating beams were fully ionized, which rendered it possible to measure pure ${\ensuremath{\beta}}^{+}$ branches for $^{52g}\mathrm{Fe}$ and $^{53g}\mathrm{Fe}$ and the sum of pure ${\ensuremath{\beta}}^{+}$ and $\ensuremath{\gamma}$ branches in the decay of the isomers $^{52m}\mathrm{Mn}$ and $^{53m}\mathrm{Fe}$.

The simultaneous direct mass measurements of 21 neutron-rich nuclei ranging from /sup 19/C to /sup 37/P have been performed with a new type of recoil spectrometer. The masses of /sup 19/C, /sup 27//sup --//sup 28/Ne, /sup 32//sup --//sup 34/Al, /sup 36/Si, and /sup 37/P have been determined for the first time. No evidence of an increase in the two-neutron separation energy as noted for /sup 31//sup --//sup 32/Na is observed for /sup 30//sup --//sup 32/Mg and /sup 32//sup --//sup 34/Al.

The nuclear charge distribution of fission products from $^{235}\mathrm{U}({n}_{\mathrm{th}}, f)$ is determined for the isobaric chains 92 to 100. The results were obtained from the energy loss of monoisobaric and monoenergetic fission products in a $\ensuremath{\Delta}E$ Si surface-barrier detector. The odd-even effect is found also in the mass chains reported here for the first time, revealing an approximately sinusoidal variation of the charge distribution width with mass.