The capture reaction 3He(c~, y)TBe has been investigated in the energy range of E .... = 107 to 1,266 keV. The 4He or 3He beams of up to 300 gA particle current were incident on 3He or 4He gas targets, respectively. The gas target systems were all of the windowless and recirculating type. Excitation functions have been obtained with the use of an extended-static gas target, while the measurements of y-ray angular distributions involved a quasi-point supersonic jet system. The determination of absolute cross sections has been carried out with both types of gas target systems. The 7-ray yields in the 3He(~, 7)7Be reaction were detected using 80 cm 3 Ge(Li) detectors. The data lead to a zero-energy intercept of the astrophysical S(E) factor of S(0)=0.30+0.03 keV-b. This result reduces the calculated solar neutrino rate by a factor of 1.76.Nuclear Reactions: 3He(~, 7)7Be, E ..... = 107 to 1,266 keV; measured o-(E, E~,, 07.); deduced spectroscopic factors and astrophysical S-factor; solar neutrino problem; extended and quasi-point jet gas targets, Ge(Li) detectors.

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The reaction ' B(p, y}"C has been investigated in the energy range E~=0.07 -2.20 MeV. The broad resonant structure previously observed in the ground state transition near E"=1. 2 MeV has been seen also in y-ray transitions to excited states. The observed excitation functions as well as the y-ray angular distributions can be explained by assuming several broad overlapping resonances.The low-energy data (Ep & 0.6 MeV) reveal the existence of two s-wave resonances at Ep =0.010 and 0.56 MeV. Spectroscopic factors for several final states have been obtained from observation of direct capture processes to them; they are in fair agreement with results from stripping reaction studies. The present data also provide information on partial and total widths of the states at E"=8 -9 MeV. The energy range investigated corresponds to the temperature range of T=(0.01 -5) &&10 K. The thermonuclear reaction rates deduced from the present results are compared with previously reported values.' NUCLEAR REACTIONS ' B(p,y), Ep =0.07 -2.20 MeV; measured y yield for ' "C states up to E"=10. 7 MeV. Deduced resonance parameters, branching ratios, and direct capture contributions for proton-unbound states; deduced spectroscopic factors, I y/I t t and I ", for several a-unbound states. Calculated thermonuclear reaction rate for T=(0.01 -5) & 10 K.

The capture reaction 4He(t2C,7)160 (E .... =l.34-3.38MeV) as welt as the elastic scattering process ~He02C,12C)4He (Ee,m. = 1.44-3.38 MeV) have been investigated with the use of an intense I2C beam and a windowless and 4He recirculating gas target system. The measurements involved two large NaI(T1) crystals in close geometry to an extended gas target, whereby angle-integrated ?-ray yields were obtained. A large area plastic detector was used for the suppression of time-independent background. A search for cascade 7-ray transitions was carried out by coincidence techniques. The measurement of absolute cross sections is also reported. Theoretical fits of the excitation function for the groundstate ?-ray transition require E1 as well as E2 capture amplitudes, which are of equal importance at stellar energies. This result increases significantly the stellar burning rate of 4He02C,7)160 and leads to 160 as the dominant product at the end of helium burning in massive stars. The observed capture yield to the 6.92 MeV state is dominated by the direct capture mechanism and plays a small role at stellar energies.Nuclear Reactions: ~He(12C,12C)4He, Ec.m. = 1.44-3.38 MeV; measured ~r(E, 0), deduced resonance parameters; 4He(12C,7)160, E .... =l.34-3.38MeV; measured a(E,E~), deduced resonance parameters, reduced alpha particle widths and astrophysical S-factor; extended gas target, NaI(T1) detectors.