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2. Recent HRIBF Research - Fusion of Mass-134 Isobars (Sn, Sb and Te) with 64Ni - First Results
(D. Shapira, spokesperson)

In the Feb. 2005 newsletter we reported our first attempt to measure the cross section of evaporation-residue production near and below the barrier in 134Sn+64Ni. At that time we were able to present the cross section of evaporation-residue production in 134Te+64Ni. In this article we present the data of combined evaporation residue production resulting from collisions between a mixture of A=134 isobars and a 64Ni target.

By repeating the same measurement with different mixtures of the three main isobars in the A=134 beam, we were able to extract cross sections for evaporation residue production from 134Sn+64Ni, 134Sb+64Ni and 134Te+64Ni collisions. The unfolding was made possible by our unique experimental setup (see Fig. 1 in the Feb. 2005 newsletter and Ref. [1]), in which we sample the beam continuously throughout the experiment during which we measure the production of evaporation residues.

Figure 2-1: The mixture of isobars in the A=134 beam as observed in two different runs.

Fig. 2-1 shows the isobar mixture from two separate runs. Since we measure near and below the barrier of the 134Sn+64Ni collision, presence of 134Ba in the mixture does not contribute to evaporation residue production and our main concern is the contributions from the Te,Sb and Sn isobars. Fig.2-2 presents cross sections for evaporation residue production of the three main components in our A=134 isobar mixture. The presentation of these data is preliminary. Because of the paucity of 134Sn+64Ni and 134Sb+64Ni data we could not apply our customary correction of the energy scale that takes account of the steep decline in cross section in the energy interval sample by the beam in the thick target. The data are presented with the beam energy fixed at the half-way point inside the target which is probably too high. We plan to take more data points along the excitation function which will enable us to apply similar correction as outlined in our publication of the 132Sn+64Ni data [2].

Figure 2-2: Cross sections of evaporation-residue productions in 134Te+64Ni, 134Sb+64Ni and 134Sn+64Ni reactions. Vertical bars indicate the locations of the Coulomb barrier in each system.

[1] Shapira et al. Nucl. Instrum. Methods Phys. Res. A551, 330 (2005).
[2] F.J. Liang et al. Phys. Rev. C75, 054607 (2007).

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