IntroductionDiscovery of 171-210HgSummaryEXPLANATION OF TABLEPreprint submitted to ATOMIC DATA AND NUCLEAR DATA TABLES August 1, 2009Discovery of the Mercury IsotopesD. MEIERFRANKENFELD and M. THOENNESSEN∗National Superconducting Cyclotron Laboratory andDepartment of Physics and Astronomy, Michigan State University,East Lansing, MI 48824, USAForty mercury isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope abrief summary of the first refereed publication, including the production and identification method, is presented.∗Corresponding author.Email address: [email protected] (M. Thoennessen).CONTENTS1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Discovery of171−210Hg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10EXPLANATION OF TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13TABLEI. Discovery of Mercury Isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14REFERENCES FOR TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161. INTRODUCTIONThe discovery of the mercury isotopes is discussed as part of the series of the discovery of iso-topes which began with the cerium isotopes in 2009 [1]. The purpose of this series is to document andsummarize the discovery of the isotopes. Guidelines for assigning credit for discovery are (1) clearidentification, either through decay-curves and relationships to other known isotopes, particle or γ-rayspectra, or unique mass and Z-identification, and (2) publication of the discovery in a refereed jour-nal. The authors and year of the first publication, the laboratory where the isotopes were produced aswell as the production and identification methods are discussed. When appropriate, references to con-ference proceedings, internal reports, and theses are included. When a discovery includes a half-lifemeasurement the measured value is compared to the currently adopted value taken from the NUBASEevaluation [2] which is based on the ENSDF database [3].2. DISCOVERY OF171−210HGForty mercury isotopes from A = 171 − 210 have been discovered so far; these include 7 stable, 26proton-rich and 7 neutron-rich isotopes. According to the HFB-14 model [4],268Hg should be the lastbound neutron-rich nucleus (265Hg is predicted to be unbound). Along the proton dripline two moreisotopes are predicted to be stable and it is estimated that seven additional nuclei beyond the protondripline could live long enough to be observed [5]. Thus, there remain 66 isotopes to be discovered.Less than 40% of all possible mercury isotopes have been produced and identified so far.Figure A summarizes the year of first discovery for all mercury isotopes identified by the methodof discovery. The range of isotopes predicted to exist is indicated on the right side of the figure. The ra-dioactive mercury isotopes were produced using fusion evaporation (FE), light-particle reactions (LP),neutron-capture (NC), spallation reactions (SP), projectile fragmentation or fission (PF), and α-decay2Mass Number (A)Year Discovered1601802002202402601920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020Fusion Evaporation (FE)Light Particle Reactions (LP)Mass Spectroscopy (MS)Spallation (SP)Neutron Capture Reactions (NC)Projectile Fragmentation (PF)Alpha Decay (AD)-9Undiscovered, predicted to be boundUndiscovered, unbound with lifetime > 10 sFIG. A. Mercury isotopes as a function of time they were discovered. The different production methodsare indicated. The solid black squares on the right hand side of the plot are isotopes predicted to bebound by the HFB-14 model. On the proton-rich side the light blue squares correspond to unboundisotopes predicted to have lifetimes larger than ∼ 10−9s.(AD). The stable isotopes were identified using mass spectroscopy (MS). Heavy ions are all nuclei withan atomic mass larger than A=4 [6]. Light particles also include neutrons produced by accelerators. Inthe following, the discovery of each mercury isotope is discussed in detail.171Hg171Hg was discovered by Kettunen et al. in 2004, and published in Decay studies of170,171Au,171−173Hg, and176Tl [7]. The cyclotron of the Accelerator Laboratory of the University of Jyv¨askyl¨ain Finland was used to produce the isotopes by the96Ru(78Kr,3n) fusion evaporation reaction. Theisotopes were separated by the gas-filled recoil separator RITU, and implanted into a position sensitivesilicon strip detector. “A new α-decaying isotope171Hg and the previously known172Hg isotope wereproduced via 3n- and 2n-fusion evaporation channels in the bombardment of the96Ru target with the378Kr ion beam.” The reported half-life of 53+36−16µs is currently the only measurement.172,173HgThe discovery by Seweryniak et al. of172Hg and173Hg was published in Decay properties of thenew isotopes172Hg and173Hg in 1999 [8]. The isotopes172Hg and173Hg were produced by the ATLASsuperconducting linear accelerator at Argonne National Laboratory by the fusion evaporation reactions,78Kr(96Ru,2n) and80Kr(96Ru,3n), respectively. To identify the mass, the isotopes were separated usingthe Argonne Fragment Mass Analyzer. Three strong lines “are also present in decays followed within100 ms by α particles corresponding to the decay of168Pt (Eα≈6.83 MeV), and thus are assignedto the decay of the previously unknown isotope172Hg.” The observation of α-radiation populating169Pt “leads to an unambiguous assignment of this group to the decay of a new isotope173Hg.” The0.25+.35−.09ms measured half-life of172Hg agrees with the adopted value of 0.29+0.23−0.08ms, while the173Hghalf-life of 0.9+0.6−0.3ms corresponds to the only measurement at the present time.174HgUusitalo et al. published the discovery of174Hg in Alpha decay of the new isotope174Hg [9] in 1997.174Hg was produced in the fusion-evaporation reaction144Sm(36Ar,6n) with beam energy between 180and 230 MeV at the University of Jyv¨askyl¨a in Finland. The isotopes were separated by the