Direct mass measurements of $^{68}\mathrm{Se}$ and $^{80}\mathrm{Y}$

Direct mass measurements of ${}^{68}{Se}$ and ${}^{80}Y$

M. B. Gómez-Hornillos, M. Chartier, W. Mittig, A. Lépine-Szily, L. Caballero, C. E. Demonchy, G. Georgiev, N. A. Orr, G. Politi, M. Rousseau, P. Roussel-Chomaz, and A. C. C. Villari

Phys. Rev. C 78, 014311 – Published 18 July 2008

Abstract

The masses of neutron-deficient nuclides near the $N = Z$ line with $A = 64 − 80$ have been determined using a direct time-of-flight technique which employed a cyclotron as a high-resolution spectrometer. The measured atomic masses for ${}^{68}{Se}$ and ${}^{80}Y$ were 67.9421(3) u and 79.9344(2) u, respectively. The new values agree with the 2003 Atomic Mass Evaluation. The result for ${}^{68}{Se}$ confirms that this nucleus is a waiting point of the rp-process, and that for ${}^{80}Y$ resolves the conflict between earlier measurements. Using the present results and the 2003 Atomic Mass Evaluation compilation, the empirical interaction between the last proton and the last neutron in $N = Z$ nuclei has been revisited and extended.

Received 9 November 2006

DOI:https://doi.org/10.1103/PhysRevC.78.014311

Authors & Affiliations

M. B. Gómez-Hornillos^1,2,*, M. Chartier^1,†, W. Mittig^3,‡, A. Lépine-Szily⁴, L. Caballero⁵, C. E. Demonchy^1,3,§, G. Georgiev^3,∥, N. A. Orr⁶, G. Politi⁷, M. Rousseau^3,¶, P. Roussel-Chomaz³, and A. C. C. Villari^3,**

¹Physics Department, University of Liverpool, Oliver Lodge Laboratory, Liverpool L69 7ZE, United Kingdom
²STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, United Kingdom
³Grand Accélérateur National d'Ions Lourds, Boulevard Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France
⁴Instituto de Fisica, Universidade de São Paulo, C.P. 66318, 05315-970 São Paulo, Brazil
⁵IFIC, CSIC-Universidad de Valencia, E-46071 Valencia, Spain
⁶LPC-Caen, ENSICAEN, Université de Caen et IN2P3-CNRS, F-14050 Caen Cedex, France
⁷Dipartimento di Fisica e Astronomia dell'Università di Catania, 64 Via S. Sofia, I-95123 Catania, Italy

^*Current address: SEN, Universitat Politècnica de Catalunya, ETSEIB, 08028 Barcelona, Spain.
^†Corresponding author: Dr M. Chartier, University of Liverpool, E-mail:chartier@liverpool.ac.uk, Tel: +44 (0)151 794 6775, Fax: +44 (0)151 794 3348.
^‡NSCL, Michigan State University, 1 Cyclotron, East Lansing, Michigan 48824-1321, USA.
^§Current address: CENBG, Le Haut-Vigneau, F-33175 Gradignan, France.
^∥Current address: CSNSM, 91405 Orsay Campus, France.
^¶Current address: IPHC-Strasbourg, 23, Rue du Loess, BP 28, F-67037 Strasbourg, France.
^**Current address: PANTECHNIK S.A., 13, Rue de la Resistance, F-14400 Bayeux, France.

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Vol. 78, Iss. 1 — July 2008

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Figure 1
Two-dimensional plot of total energy deposited in the silicon-detector telescope vs the phase of the detected ions obtained using the $^{nat}$ Mg target. The different mass regions, as indicated, are clearly separated.Reuse & Permissions
Figure 2
Two-dimensional plot of number of turns intercepted in the silicon-detector telescope vs the phase of the detected ions, gated on the mass region $A = 76$ of Fig. 1. The isobars ${}^{76}{Rb}$ and ${}^{76}{Kr}$ are clearly separated. The $V$ shape of the ${}^{76}{Rb}$ ions distribution is discussed in the text.Reuse & Permissions
Figure 3
Tabulated relative $m / q$ differences with respect to ${}^{80}{Sr}$ $^{20 +}$ , from AME03 [13], vs the measured phase for each ion species with both Mg targets. The fits obtained using second-order polynomials [Eq. (4)] are shown for each data set. The reference masses are represented by color symbols (horizontal and vertical error bars have been taken into account). The data points for ${}^{68}{Se}$ and ${}^{80}Y$ (black stars) are not included in the fits. Each color represents a different value of the cyclotron magnetic field, increasing from left to right; and each type of symbol represents a different radial position of the detector, decreasing from left to right (for each magnetic field setting). The filled symbols correspond to the $^{nat}$ Mg target and the empty symbols to the ${}^{24}{Mg}$ .Reuse & Permissions
Figure 4
Tabulated relative $m / q$ differences with respect to ${}^{80}{Sr}$ $^{20 +}$ , from AME03 [13], vs the measured phase for each ion species. The same colors and symbols codes apply as in Fig. 3. The plot shows the nine selected fits and the seven data points for ${}^{68}{Se}$ $^{17 +}$ and ${}^{80}Y$ $^{20 +}$ (in the same phase region as ${}^{80}{Sr}$ $^{20 +}$ , as indicated by the vertical lines) used for the local slope analysis (see text).Reuse & Permissions
Figure 5
Calculated effective half-life of ${}^{68}{Se}$ (black curve) as a function of $Q_{p}$ ( ${}^{68}{Se}$ ), along with different experimental $Q_{p}$ ( ${}^{68}{Se}$ ) values from Table (see text).Reuse & Permissions
Figure 6
Values of $δ V_{pn}$ calculated from Eqs. (1) and (2) for even-even and odd-odd systems, respectively, as a function of $A$ (for $A ⩾ 15$ ). The binding energies used in the calculations are the experimental values quoted in AME95 [42] and AME03 [13] represented by filled triangles ( $N = Z$ ) and circles ( $N \neq Z$ ). The open triangles show data in which the binding energy for the $N < Z$ member of the quartet is calculated with a correction for the Coulomb energy difference from the mass of its mirror nucleus (see text). The stars show data where more than one of the binding energies in the calculation was obtained from mass-systematics values. The vertical line indicates the highest mass number at which all four values of the binding energies are experimental in the AME95 table.Reuse & Permissions

Physical Review C

covering nuclear physics

Direct mass measurements of ${}^{68}{Se}$ and ${}^{80}Y$

M. B. Gómez-Hornillos, M. Chartier, W. Mittig, A. Lépine-Szily, L. Caballero, C. E. Demonchy, G. Georgiev, N. A. Orr, G. Politi, M. Rousseau, P. Roussel-Chomaz, and A. C. C. Villari

Phys. Rev. C 78, 014311 – Published 18 July 2008

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Physical Review C

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Direct mass measurements of Se68 and Y80

M. B. Gómez-Hornillos, M. Chartier, W. Mittig, A. Lépine-Szily, L. Caballero, C. E. Demonchy, G. Georgiev, N. A. Orr, G. Politi, M. Rousseau, P. Roussel-Chomaz, and A. C. C. Villari

Phys. Rev. C 78, 014311 – Published 18 July 2008

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Direct mass measurements of ${}^{68}{Se}$ and ${}^{80}Y$