We have measured the Coulomb dissociation of 8 B into 7 Be and proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical S17 factor for the 7 Be (p,γ) 8 B reaction at Ec.m. = 0.25 − 2.78 MeV is deduced yielding S17(0) = 20.6±1.2 (exp.) ± 1.0 (theo.) eV-b. This result agrees with the presently adopted zero-energy S17 factor obtained in direct-reaction measurements and with the results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon. PACs: 25.40.Lw, 25.70.De, 26.65.+t The precise knowledge of the solar thermonuclear fusion of 8 B (from 7 Be plus proton) is crucial for estimating the 8 B solar neutrino flux and the predicted neutrino rates in terrestrial neutrino measurements. The relevant 7 Be(p,γ) 8 B cross section σ(E) is parameterized in terms of the astrophysical factor S 17 (E) which is defined by2 /hv is the Sommerfeld parameter. The flux of 8 B solar neutrinos is particularly important for the results of the Homestake, Super Kamiokande, and SNO experiments [1] which measure high-energy solar neutrinos mainly or solely from the 8 B decay. Unfortunately, this cross section has not been known with sufficient accuracy for a long time, despite the fact that several comprehensive direct measurements were reported for the 7 Be(p,γ) 8 B reaction [2][3][4][5][6]. The main difficulty in such experiments is the determination of the effective target thickness of the radioactive 7 Be target. This difficulty is reflected in the fact that the results of these measurements can be grouped into two distinct data sets which agree in their energy dependence but disagree in their absolute normalization by about 30%. In view of this discrepancy, experimental studies with different methods are highly desirable.As an alternative approach one can measure the inverse process, the Coulomb dissociation (CD) of 8 B into 7 Be and proton [7]. The CD yields are enhanced because thicker targets can be used and a larger phase space is available for CD. This method uses stable targets and thus is free from the difficulty of determining the effective target thickness. On the other hand, direct (p,γ) and Coulomb dissociation measurements have different sensitivities to the multipole composition of the photon fields. The E2 amplitude is enhanced in CD due to the large flux of E2 virtual photons, whereas it can be neglected in the (p,γ) reaction.Recently, Motobayashi et al. have performed a CD experiment at E( 8 B) = 46.5 MeV/nucleon, yielding values for S 17 in the energy range 0.6−1.7 MeV [8]. The extracted (p,γ) cross section is consistent with the results from the lower group of direct-reaction data points [4][5][6]. Another measurement at 51.9 MeV/nucleon by the same group with improved accuracy led essentially to the same conclusion [9].In this article, we report on an experiment of the CD of 8 B at a higher energy of 254 MeV/nucleon performed at the SIS facility at GSI, Darmstadt, Germany. The present incident energy has several advantages compared to those used in Refs. ...

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A primary beam of 58 Ni at 600 MeV͞nucleon from the SIS synchrotron at GSI was used to produce proton-rich isotopes in the titanium-to-nickel region by projectile fragmention on a beryllium target. The fragments were separated by a projectile-fragement separator and unambiguously identified. We report here the first observation of the T z 27͞2 nuclei 45 Fe and 49 Ni, the most protonrich nuclei ever synthesized with an excess of seven protons. In addition, the new isotope 42 Cr ͑T z 23͒ was identified. According to commonly used mass predictions, these isotopes are all unbound with respect to two-proton emission from their ground states. From the nonobservation of 38 Ti ͑T z 23͒ in this experiment, an upper limit of 120 ns is deduced for the half-life of this isotope. [S0031-9007(96)

23 Si isotopes have been produced as projectile fragments of a 36 Ar primary beam at 95 MeV/nucleon at the LISE3 spectrometer of GANIL. After implantation in a detector telescope, β-delayed one-proton and β-delayed two-proton emission has been observed. The main one-proton peaks are at (1.32±0.04)MeV, (2.40±0.04)MeV, and (2.83±0.06)MeV. The total decay energy for the β2p decay is (6.18±0.10)MeV for the decay to the ground state and (5.86±0.10)MeV for the decay to the first excited state in the daughter nucleus. However, energetically possible decays via βpα and β3p emission have not been identified. The spectra allowed us to determine the excitation energy of the isobaric analogue state in 23 Al. This enabled us to calculate the coefficients of the T = 5/2 isobaric multiplet mass equation for A = 23. The mass excess of the 23 Si ground state was deduced. This value is compared to different theoretical predictions. Additionally, we determined the branching ratios for the different decay branches. A halflife measurement yielded T 1/2 = (40.7±0.4)ms.

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