| Project/Area Number |
62540198
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
IKEDA Akitsu Dept. of Phys., Tokyo Inst. of Tech., Assistant, 理学部物理, 助手 (40016126)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Hiroshi Dept. of Phys., Tokyo Inst. of Tech., Professor, 理学部物理, 教授 (90108192)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | Nuclear Rotational Motion / Particle-Rotor Model / Signature-dependence / Signature Inversion / Triaxial Deformation / 回転整列 / 粒子-回転子結合模型 |
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| Research Abstract |
The quantum number called "signature" represents an important concept for rotational bands of odd-mass nuclides. It is derived from the invariance of the hamiltonian under rotation by 180 degrees around an principal axis of the deformed nucleus. Signature splits a rotational band of an odd-mass nucleus into two groups,which are shifted in energy with respect to each other. M1 transitions connecting the two groups depend on signature in a characteristic manner. These signature-dependences are well understood in terms of the Coriolis force in the particle-rotor model. However counterexamples against this well-understood physics have been discovered in odd-mass Ho, Tm and Lu isotopes: the energy spectra depend on signature in the opposite way. This is called the problem of signature-inversion and the main purpose of this project to solve it.
There has been a theoretical proposal which asserts that this can be explained by assuming the rotation of a triaxially deformed nuclear system around the shortest axis. I think this idea may have difficulty in explaining some features of the experimental data and have looked for a different soulution.I have found that the signature-inversion can be well reproduced in the particle plus axial-symmetric-rotor model if the gammavibrational excitation is taken into account and if such a set of moments of inertia are employed that favor the rotation around the shortest axis. On top of the energy spectra I have calculated M1 and E2 transition probabilities and obtained very good reproduction of all the available experimental data. I have found that the model can be improved in the quantitative sense by taking the beta-vibration into account, and am developing a more general model which includes the beta- and gamma-vibrations.
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