Number 230, June 14, 1995 by Phillip F. Schewe and Ben Stein HYPERDEFORMED NUCLEI even more distorted than superdeformed nuclei have been found in recent experiments at Lawrence Berkeley Laboratory. When two medium-sized nuclei collide off-center, they can fuse into a highly-spinning, distorted nucleus which then sheds its rotational energy by emitting a series of gamma rays. In the past few years, researchers have found numerous examples of superdeformed nuclei, football-shaped particles with a 2-to-1 long-to-short axis ratio. But in recent experiments at LBL's 88-Inch Cyclotron, even more oblong (3-to-1) nuclei have apparently been produced. Demetrios Sarantites (314-935-6504) of Washington University in St. Louis and his colleagues smashed a 230-MeV beam of vanadium-51 nuclei into a molybdenum-100 foil. Gamma rays and charged particles, detected by LBL's Gammasphere and Microball arrays respectively, suggested the existence of hyperdeformed gadolinium-147 nuclei. The existence of such nuclear states challenges the current understanding of fission and fusion in nuclei with very high angular momentum. One might expect such highly spinning nuclei to fragment immediately into two smaller pieces. Instead, a very small fraction of the hyperdeformed nuclei remain intact and merely get rid of their spins by emitting gamma rays. (D.R. LaFosse et al., to appear in Physical Review Letters, 26 June 1995.) AN ACCELERATION GRADIENT OF 30 GeV/m has been achieved by scientists from a consortium of labs in Japan. The researchers used short (1 psec) and powerful (3 TW) laser pulses to excite waves in a plasma. Electrons which had been injected into the plasma at an energy of 1 MeV were then accelerated up to an energy of 25 MeV, all in a space of less than 1 mm, for a net gradient of 30 GeV/m. For such ultrahigh acceleration gradients to be useful for particle physics applications (squeezing the milelong SLAC accelerator, say, into a space of only a few meters), the whole process would have to be scaled up considerably. (K. Nakajima et al., Physical Review Letters, 29 May 1995.) THE MOST ELONGATED SOLAR SYSTEM OBJECT YET IMAGED is the asteroid 1620 Geographos. Like the most oblong nucleus described in the paragraph above, the pototo-shaped Geographos has an aspect ratio (length/width) of about 3 (2.76 to be exact). The 5-km Geographos, which passed to within 0.034 astronomical units of Earth in August 1994, was photographed at radar wavelengths by Caltech astronomers. Small asteroids are generally thought to be the result of the breakup or collision of larger bodies. Laboratory fragmentation studies suggest the average aspect ratio for pieces should be 1.4. Only 1% of fragments should be as oblong as Geographos. (S.J. Ostro et al., Nature, 8 June 1995.) REMINDER ON SUBSCRIBING TO PHYSICS NEWS UPDATE: You can automatically subscribe or unsubscribe by sending a message to listserv@aip.org (and not physnews@aip.org). Leave the "subject" line blank, and for the message merely specify "add physnews" or "delete physnews". This will serve to add to or delete the address that appears in the header information from the Update distribution list.