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Theses

Optimized ion trapping of exotic nuclides for mass
measurements in the N=40 (magic?) region

Abstract : Magic numbers or shell closures, are an important feature of nuclear structure, but now found to be modified far from stability. Determination of the nuclear binding energy via mass measurements of exotic nuclides represents one of the greatest challenges in the
study of nuclear structure due to the high precision required and the low production rates and short half-lives. To solve the problem, the complementary spectrometers MISTRAL and ISOLTRAP may be used, both located at ISOLDE/CERN (Geneva). MISTRAL is a transmission mass spectrometer for very short-lived nuclides, and ISOLTRAP a Penningtrap mass spectrometer providing exceptional precision. This thesis describes improvements in the limitations of these complementary instruments: a beam cooler to increase the sensitivity of MISTRAL and an optimization procedure to improve the definition of the ISOLTRAP trapping fields. High-precision mass measurements were performed at ISOLTRAP to extend the backbone of well-known nuclides in the mass table, and to finely examine the case for new magic numbers N = 32 and 40. The results illustrate a subtle effect of extra binding energy for 56Cr32 in the presence of a probable deformation. A small effect is visible for 68Ni40, perhaps in conjunction with a competitive mid-shell effect at N = 39, the case for a shell or even sub-shell closure at N = 40 is excluded by these results.
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Submitted on : Monday, February 13, 2006 - 2:36:42 PM
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C. Guénaut. Optimized ion trapping of exotic nuclides for mass
measurements in the N=40 (magic?) region. Nuclear Theory [nucl-th]. Université Paris Sud - Paris XI, 2005. English. ⟨tel-00011595⟩

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