High-precision mass measurements of nickel, copper, and gallium isotopes and the purported shell closure at N = 40

High-precision mass measurements of more than 30 neutron-rich nuclides around the Z=28 closed proton shell were performed with the triple-trap mass spectrometer ISOLTRAP at ISOLDE/CERN to address the question of a possible neutron shell closure at N=40. The results for {sup 57,60,64-69}Ni (Z=28), {sup 65-74,76}Cu (Z=29), and {sup 63-65,68-78}Ga (Z=31) have a relative uncertainty of the order of 10{sup -8}. In particular, the mass of {sup 76}Cu was measured for the first time. We analyze the resulting mass surface for signs of magicity, comparing the behavior of N=40 with that of known magic numbers and with midshell behavior. While the classic indications from the mass surface show no evidence for a shell closure at N=40, there is evidence for a weak--and very localized--effect for Z=28, consistent with findings from nuclear spectroscopy studies.

[1]  J. Delaroche,et al.  Structure properties of even–even actinides at normal and super deformed shapes analysed using the Gogny force , 2006 .

[2]  Klaus Blaum,et al.  High-accuracy mass spectrometry with stored ions , 2006 .

[3]  P. Bonche,et al.  Solution of the Skyrme HF+BCS equation on a 3D mesh , 2005, Comput. Phys. Commun..

[4]  S. Goriely,et al.  Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. IV: Neutron-matter constraint , 2005 .

[5]  G. Bertsch,et al.  Systematics of quadrupolar correlation energies. , 2004, Physical review letters.

[6]  F. Nowacki,et al.  The shell model as a unified view of nuclear structure , 2004, nucl-th/0402046.

[7]  S. Goriely,et al.  Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. III: Role of particle-number projection , 2004, nucl-th/0409006.

[8]  Klaus Blaum,et al.  Population inversion of nuclear states by a Penning trap mass spectrometer , 2004 .

[9]  A. H. Wapstra,et al.  The AME2003 atomic mass evaluation . (II). Tables, graphs and references , 2003 .

[10]  A. H. Wapstra,et al.  The Ame2003 atomic mass evaluation: (I). Evaluation of input data, adjustment procedures☆ , 2003 .

[11]  M. Bender,et al.  Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. II: Role of the effective mass , 2003, nucl-th/0311086.

[12]  B. A. Brown,et al.  β-decay properties ofTi55,56 , 2003 .

[13]  Stéphane Goriely,et al.  Further explorations of Skyrme–Hartree–Fock–Bogoliubov mass formulas: I: Role of density dependence in pairing force , 2003 .

[14]  D. Lunney,et al.  Recent trends in the determination of nuclear masses , 2003 .

[15]  K. Blaum,et al.  Recent developments at ISOLTRAP: towards a relative mass accuracy of exotic nuclei below 10−8 , 2003 .

[16]  W. Nazarewicz,et al.  How magic is the magic 68 Ni nucleus , 2002, nucl-th/0210089.

[17]  E. Sauvan,et al.  From direct to absolute mass measurements: A study of the accuracy of ISOLTRAP , 2003 .

[18]  S. Goriely,et al.  Hartree-Fock mass formulas and extrapolation to new mass data , 2002 .

[19]  A. Kellerbauer,et al.  A linear radiofrequency quadrupole ion trap for the cooling and bunching of radioactive ion beams , 2002 .

[20]  S. Goriely,et al.  A Hartree-Fock-Bogoliubov mass formula , 2002 .

[21]  T. Teranishi,et al.  Isomeric 0+ state in 12Be , 2001 .

[22]  F. Ames,et al.  Accurate masses of neutron-deficient nuclides close to Z=82 , 2001 .

[23]  Matthew W. Cooper,et al.  New evidence for a subshell gap at N=32 , 2001 .

[24]  Stéphane Goriely,et al.  A Hartree-Fock Nuclear Mass Table , 2001 .

[25]  A. Kellerbauer,et al.  A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams , 2000, nucl-ex/0011021.

[26]  J. Pearson.  The Quest for a Microscopic Nuclear Mass Formula , 2001 .

[27]  E. Kugler,et al.  The ISOLDE facility , 2000 .

[28]  S. Goriely,et al.  Towards a Hartree-Fock mass formula , 2000 .

[29]  Suzuki,et al.  New magic number, N = 16, near the neutron drip line , 2000, Physical review letters.

[30]  Z. Ren,et al.  Shape coexistence and the N = 28 shell closure far from stability , 2000 .

[31]  D. Pritchard,et al.  Penning Trap Measurements of the Masses of C133s, R87,85b, and N23a with Uncertainties ≤0.2 ppb , 1999 .

[32]  K. Kratz,et al.  Magicity of the 68 Ni Semidouble-Closed-Shell Nucleus Probed by Gamow-Teller Decay of the Odd- A Neighbors , 1999 .

[33]  J. Delaroche,et al.  Microscopic descriptions of superdeformed bands with the Gogny force: Configuration mixing calculations in the A~190 mass region , 1999 .

[34]  J. Duflo,et al.  The nuclear monopole Hamiltonian , 1999 .

[35]  Y. Jading,et al.  Decay of neutron-rich Mn nuclides and deformation of heavy Fe isotopes , 1998, nucl-ex/9812008.

[36]  M. Hjorth-Jensen,et al.  NEW ISLAND OF MU S ISOMERS IN NEUTRON-RICH NUCLEI AROUND THE Z = 28 AND N = 40 SHELL CLOSURES , 1998 .

[37]  D. Beck,et al.  A cylindrical Penning trap for capture, mass selective cooling, and bunching of radioactive ion beams , 1997 .

[38]  Lutz Schweikhard,et al.  ISOLTRAP: a tandem Penning trap system for accurate on-line mass determination of short-lived isotopes , 1996 .

[39]  A. H. Wapstra,et al.  The 1995 update to the atomic mass evaluation , 1995 .

[40]  P. Heenen,et al.  Microscopic study of superdeformation in 193Hg , 1995 .

[41]  H. Kluge,et al.  Quadrupole excitation of stored ion motion at the true cyclotron frequency , 1995 .

[42]  Rico,et al.  N=40 neutron subshell closure in the 68Ni nucleus. , 1995, Physical review letters.

[43]  W. Myers,et al.  Nuclear ground state masses and deformations , 1995 .

[44]  N. Perrin,et al.  Evidence for gamma vibrations and shape evolutions through the transitional Hg-184, Hg-186, Hg-188, Hg-190 nuclei , 1994 .

[45]  G. W. Butler,et al.  Mass measurement of neutron-rich isotopes from51Ca to72Ni , 1994 .

[46]  H. Kluge,et al.  Towards a "perfect" Penning trap mass spectrometer for unstable isotopes , 1992 .

[47]  L. Ekström,et al.  Nuclear data sheets for A = 90 , 1992 .

[48]  G. Bollen,et al.  A new cooling technique for heavy ions in a Penning trap , 1991 .

[49]  J. F. Berger,et al.  Time-dependent quantum collective dynamics applied to nuclear fission , 1991 .

[50]  Becker,et al.  Accurate mass determination of short-lived isotopes by a tandem Penning-trap mass spectrometer. , 1990, Physical review letters.

[51]  G. Bollen,et al.  The accuracy of heavy‐ion mass measurements using time of flight‐ion cyclotron resonance in a Penning trap , 1990 .

[52]  J. Dobaczewski,et al.  Analysis of the generator coordinate method in a study of shape isomerism in 194Hg , 1990 .

[53]  Lowell S. Brown,et al.  Geonium theory: Physics of a single electron or ion in a Penning trap , 1986 .

[54]  P. Dessagne,et al.  The complex transfer reaction (14C, 15O) on Ni, Zn and Ge targets: Existence and mass of 69Ni , 1984 .

[55]  F. Touchard,et al.  β-Decay schemes of very neutron-rich sodium isotopes and their descendants , 1984 .

[56]  B. Grammaticos,et al.  Triaxial Hartree-Fock-Bogolyubov calculations with D-1 effective interaction , 1983 .

[57]  P. Dessagne,et al.  Magic features of 68Ni , 1982 .

[58]  J. Dechargé,et al.  Hartree-Fock-Bogolyubov calculations with the D 1 effective interaction on spherical nuclei , 1980 .

[59]  H. Kalinowsky,et al.  A direct determination of the proton electron mass ratio , 1980 .

[60]  M. S. Weiss,et al.  Three-dimensional time-dependent Hartree-Fock calculations: Application to 16O + 16O collisions , 1978 .

[61]  A. Poskanzer,et al.  Direct measurement of the masses of Li 11 and Na 2 6 − 3 2 with an on-line mass spectrometer , 1975 .

[62]  W. D. Myers,et al.  NUCLEAR MASSES AND DEFORMATIONS , 1966 .

[63]  L. Cooper,et al.  Theory of superconductivity , 1957 .

[64]  Hans A. Bethe,et al.  Nuclear Physics A. Stationary States of Nuclei , 1936 .

[65]  C. Weizsäcker.  Zur Theorie der Kernmassen , 1935 .