DISCOVERY OF SOFT DIPOLE RESONANCE IN HELIUM-6. In some neutron-rich nuclei extra neutrons can constitute a "halo" or satellite nucleus. Furthermore, when these compound nuclei are excited the parts oscillate back and forth. For example, in the case of lithium-6, the three protons can oscillate together opposite the three neutrons (an arrangement called "giant dipole resonance" or GDR). I

n the case of helium-6, one expects that an oscillating resonance should occur in which one unit, consisting of two protons and two neutrons (an alpha particle, in other words), moves in opposition to a unit made of two neutrons (see figure at Physics News Graphics).

However, vigorous experimental work had up to now failed to find the oscillation, and physicists had begun to doubt its existence. This long-looked-for "soft dipole resonance" has now been observed for the first time by a Tokushima-Konan-RCNP-Osaka collaboration of physicists in Japan (Shintaro Nakayama, nakayama@ias.tokushima-u.ac.jp, 011-81-88-656-7236). They created the He-6 resonance when a Li-7 beam struck a target of Li-6 atoms. (Nakayama et al., Physical Review Letters, 10 July; Select Articles.)