hydrogen events" were examined under high magnification to determine whether one or more light tracks were also associated. One example of a pair of light tracks, assumed to be electrons, was found (Fig. 1). s'~e++e +y.(2) followed by the direct decay of the neutral pion, as predicted by Dalitz4 and as observed by various authors'' CpĨ t~P rocess (1) is the charge-symmetric analog of the process which was used to explain the pairs in the negative pion beam: s. +~'+e.(3)Since there are approximately as many neutrons as protons in the emulsion the cross sections for (1) and (3) should be nearly the same, which is not inconsistent with the results reported here. The lack of a visible gap between the pair and the star is in agreement with the short lifetime reported earlier. FIG. 1. Electron pair produced by 113-Mev positive pion: u, incident pion; b, proton of 75&10 Mev or other fragment of same ionization; c1, c2 electrons of 27&9 and 56&14 Mev, respectively.The angle between the two electron tracks 8 is 5.2 1. 0' and the angle between the direction of the incident pion and the direction of the center of mass of the pair p is 62&2'. The energies of the two electrons are 27~9 Mev and 56&14 Mev. These data are consistent with the earlier results obtained on the negativepion-produced pairs' except for the angle g, which is smaller than any of the angles reported earlier and which seemed in the earlier work to have an improbably sharp distribution centered around 115' in the laboratory system. Since this is the only case in the positive beam, the significance of the occurrence of such an angle is not clear. In the area scanned for this experiment, there were (1.56+0.05)&&10' cm of pion track. ' Since the mean free path for pions at very nearly the same energy' is 33.6&17 cm, approximately 4600 interactions must have occurred. Approximately one-eighth of these would be "possible hydrogen events" as described earlier. Thus one pair was found in about 600 stars examined. There is no visible gap on this pair, and a gap would have been seen if it were as large as one micron. It is suggested that this pair can be interpreted as the result of the charge-exchange scattering of a pion on a neutron in a nucleus of the emulsion: vr++ m -+n'+ p, HERE are experimental' ' and theoretical~' indications of a state in Al" lying below the 6-second positron-emitting 0+ state. The ground state apparently4' lies 4.0 Mev above that of Mg" and is expected~to have a 5+ configuration. If the Mg' states at 1.83 and 2.97 Mev" both have 2+ configurations,Ap" should decay predominantly by positron emission to the 1.83-Mev state with a half-life estimated'' at 10' -10' years, with smaller amounts of electron capture to both states. We have sought radioactivity in aluminum carrier isolated from a target of commercial magnesium bombarded with 400 pa-hr of 15-Mev deuterons in the University of Pittsburgh cyclotron. After numerous NH4OH precipitations at pH 6, numerous NaOH precipitations of Fe(OH). -, and two 8-hydroxyquinoline precipi. tations, the a...

The compression-mode isoscalar giant monopole resonance (ISGMR) has been studied in the Sn, Cd and Pb isotopes using inelastic scattering of 400 MeV α-particles at extreme forward angles, including .We have obtained completely ``background-free'' inelastic-scattering spectra for the Sn, Cd, and Pb isotopes for a wide angular and excitation-energy range. The various giant resonances excited with different transferred angular momenta were extracted by a multipole-decomposition analysis (MDA). It was found that the centroid energies of the ISGMR in Sn isotopes are significantly lower than the theoretical predictions. The K τ in the empirical expression for the nuclear incompressibility has been determined to be MeV from the moment ratios [1]. The extracted value for the Cd isotopes isMeV. These numbers are consistent with values of MeV obtained from an analysis of the isotopic transport ratios in medium-energy heavy-ion reactions [2], MeV obtained from constraints placed by neutron-skin data from anti-protonic atoms across the mass table [3], and MeV obtained from theoretical calculations using different Skyrme interactions and relativistic mean field (RMF) Lagrangians [4].Stringent constraints on interactions employed in nuclear structure calculations are obtained on the basis of the experimentally determined values for and . These parameters constrain as well the equation of state (EOS) of nuclear matter. However, a significant discrepancy still remains. The ISGMR positions in Sn and Cd isotopes are systematically lower than the predictions obtained on basis of determined from the ISGMR in 208 Pb. This raises the question "why are Sn and Cd nuclei so soft?", an important problem that has to be solved [5]. For a clue to solve the problem, the exact positions of the ISGMR in 204, 206, 208 Pb have to be measured [6].In this talk, we will review the current status of the experimental studies on the compressionmode giant resonances, and the possible implications for astrophysics and physics with exotic nuclei.[1] T. Li et al., Phys.