Mass measurements of highly neutron-excess nuclei in the light elements

Thesis/Dissertation · Thu May 01 00:00:00 EDT 1975

DOI:https://doi.org/10.2172/4136568· OSTI ID:4136568

Wilcox, Kenneth Hugh ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The ²⁶Mg(⁷Li,⁸B)²⁵Ne reaction at 78.9 MeV was used to measure the mass-excess of ²⁵Ne (-2.18 ± 0.10 MeV) and several low- lying excited states. Mass-excesses for ⁴³Ar (-31.98 ± 0.07 MeV), ⁴⁵Ar (-29.727 ± 0.06 MeV), and ⁴⁶Ar (-29.732 ± 0.07 MeV) were determined from the ⁴⁸Ca(α,⁹,⁷Be)⁴³,⁴⁵Ar reactions at 77.7 MeV and the ⁴⁸Ca(⁶Li,⁸B)⁴⁶Ar reaction at 80.1 MeV. Several excited states of ⁴³Ar and ⁴⁵Ar were observed. These and the excited states of ²⁵Ne are compared with theoretical predictions. Ground state differential cross sections are given for all reactions, ranging from 0.1 to 1 μb/sr at forward angles. Upper limits of about 1 to 25 nb/sr were determined for the ground state cross sections of the reactions ⁴⁸Ca(α,⁸,¹⁰,¹¹B)⁴⁴,⁴²,⁴¹Cl and ⁴⁸Ca(α,¹⁰-¹³C)⁴²-³⁹S at 110 MeV. Recoil coincidence techniques were used to measure the mass-excess of the particle- unbound nucleus ¹⁰Li(33.83 ± 0.25 MeV) by the ⁹Be(⁹Be,⁸B)¹⁰Li reaction at 121 MeV; the ground state cross section was 30 nb/sr. The ¹⁴C(⁹Be,⁸B)¹⁵B reaction at 120 MeV was also investigated using coincidence techniques. Contamination problems only permitted determining a ground state cross section upper limit of 50 nb/sr. A simple mass relation is derived, similar in approach to the Garvey-Kelson method but taking more explicit account of shell effects. Comparison is made with the Garvey- Kelson relation, and predictions of masses and of the stability of neutron-excess light nuclei are given for both methods. The modified mass relation is shown to offer better account for highly neutron-excess nuclei, including the values reported here for ²⁵Ne and ⁴³,⁴⁵,⁴⁶Ar.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: US Energy Research and Development Administration (ERDA)
• DOE Contract Number: W-7405-ENG-48
• NSA Number: NSA-33-008487
• OSTI ID: 4136568
• Report Number(s): LBL-4029
• Resource Relation: Other Information: Thesis. Orig. Receipt Date: 30-JUN-76
• Country of Publication: United States
• Language: English

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