NEWS OF THE WEEK
ELEMENT 112 New element madefromzinc and lead lement 112 has been created at Germany's Heavy-Ion Research Center (GSI), in Darmstadt. Its decay behavior strongly supports the predicted stability of atomic nuclei with a "magic" number of 162 neutrons. "If s a beautiful piece of work," com ments Nobelist Glenn T. Seaborg, associ ate director-at-large at Lawrence Berke ley National Laboratory. "It makes pos sible further experiments in heavyelement chemistry," notes chemistry professor Walter D. Loveland at Oregon State University, Corvallis. The multinational team led by GSI physicists Peter Armbruster and Sigurd Hofmann produced element 112 by fusing zinc and lead. The scientists un ambiguously detected an atom of the new element close to midnight on Feb. 9, after two weeks of bombarding a lead target with high-energy zinc at oms. The feat comes 14 months after the same group created element 111 (C&EN, Jan. 2,1995, page 7). The team separated the atom of the new element with a velocity filter known as SHIP (separator for heavyion products), explains Armbruster. A 16-strip silicon detector stopped the atom and registered its subsequent α-decay chain. The particular isotope formed has 165 neutrons. It decays after 280 micro seconds, emitting an 11.45-MeV α par ticle (4He nucleus) to form a new iso tope of element 110 with 163 neutrons. This isotope decays in 110 microsec onds, releasing an 11.08-MeV α particle to form a new isotope of hassium, with 108 protons and 161 neutrons. The hassium isotope decays after 19.7 seconds, emitting a 9.23-MeV α particle to become seaborgium, with 106 protons and 159 neutrons. After emission of more α particles, the chain ends at fermium. The longer half-life and the lower en ergy in the third decay event suggest that the nucleus of the new hassium iso tope—with its 161 neutrons—is more
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FEBRUARY 26,1996 C&EN
Earlier experiments with nuclei of lower atomic numbers have hinted at the stability of 162-neutron shells, Loveland says. But, Seaborg notes, this is the first clear-cut demonstration. According to GSI, the team will not propose a name for element 112 until the continuing con troversy over the names of elements 104 through 109 clears. Maureen Rouhi
Dow Coming asks judge to appoint expert panel Dow Corning is confident that inde pendent scientific experts will find no connection between silicone gel breast implants and disease. It is so confident, in fact, that it has asked a bankruptcy court judge to appoint a panel of three Armbruster: observations indicate closed shell scientists to advise the court and help stable than its predecessors. "Thaf s a determine the value, if any, of plain beautiful confirmation of a closed sub- tiffs' claims against the company. shell at 162 neutrons," Seaborg says. Dow Corning filed the motions con Scientists believe atomic nuclei have taining the request with Judge Arthur J. special stability if they have "magic" Spector of the U.S. District Court for the numbers of protons and neutrons cor Eastern District of Michigan, Northern responding to closed shells. The idea Division, Bay City, Mich. If Spector rules parallels that of closed-shell electron in favor of Dow Coming's motions at a configurations making atoms such as hearing that could come next month, he would establish ground rules for further the noble gases inert. The heaviest natural element with a hearings that could begin in September closed-shell nucleus is lead, with 82 to determine the overall value of wom protons and 126 neutrons. Scientists en's claims against the company. An es have been predicting the next closed timate of the value of such claims is one shell is at 114 protons and 184 neu step the company must complete as it trons—the much-touted island of sta attempts to emerge from bankruptcy. bility—although new estimates now "We recognize that Dow Coming's predict the closed shell is at 178 neu view of the scientific evidence differs trons. More recent theories also suggest from our critics' view," says Chairman a closed shell at 162 neutrons. "The de and Chief Executive Officer Richard A. cay chain we observed indicates this Hazleton. "This unique approach fo shell closure," Armbruster says. cused on the merits of the evidence is Seaborg expresses "delight" over the fairest way to resolve this fundamen these results. Although the longer lived tal dispute." hassium isotope has one neutron less Dow Corning says it believes the sci than predicted by theory, the magic entific experts would evaluate all med number 162 is within reach: "161 is just ical studies to date and find that im as good," he says. plants do not cause disease. Dow Corn-
