A collective model is proposed to describe the chiral rotation and vibration and applied to a system with one h 11/2 proton particle and one h 11/2 neutron hole coupled to a triaxial rigid rotor.The collective Hamiltonian is constructed from the potential energy and mass parameter obtained in the tilted axis cranking approach. By diagonalizing the collective Hamiltonian with a box boundary condition, it is found that for the chiral rotation, the partner states become more degenerate with the increase of the cranking frequency, and for the chiral vibrations, their important roles for the collective excitation are revealed at the beginning of the chiral rotation region.

Three sets of chiral doublet band structures have been identified in the 103 Rh nucleus. The properties of the observed chiral doublet bands are in good agreement with theoretical results obtained using constrained covariant density functional theory and particle rotor model calculations. Two of them belong to an identical configuration, and provide the first experimental evidence for a novel type of multiple chiral doublets, where an "excited" chiral doublet of a configuration is seen together with the "yrast" one. This observation shows that the chiral geometry in nuclei can be robust against the increase of the intrinsic excitation energy.PACS numbers: 21.10. Hw,21.10.Re,23.20.Lv A novel form of spontaneous symmetry breaking, the chiral rotation of triaxial nuclei, was suggested in 1997 [1]. It was shown that in special circumstances, referred to as chiral geometry, in the intrinsic frame of the rotating triaxial nucleus the total angular momentum vector lies outside the three principal planes. Thus, its components along the principal axes can be oriented in leftand right-handed ways. In the laboratory frame the chiral symmetry is restored, which manifests itself as a pair of ∆I = 1 nearly degenerate bands with the same parity. Such chiral doublet bands were first identified in four N = 75 isotones in 2001 [2]. So far, many chiral candidate nuclei have been reported experimentally in the A ∼ 80, 100, 130, and 190 mass regions [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Besides the simplest chiral configurations composed of one unpaired proton and neutron, composite chiral configurations, containing more than one unpaired protons and/or neutrons, have also been observed in the odd-mass or even-even neighbors of the odd-odd chiral nuclei [10,18]. These observations show that chirality is not restricted to a certain configuration in a mass region, i.e. the chiral geometry can be robust against the change of configuration. It was even demonstrated recently by Meng et al. [22][23][24][25], based on adiabatic and configuration-fixed constrained triaxial covariant density functional theory (CDFT) calculations, that it is possible to have multiple pairs of chiral doublet bands in a single nucleus, and the acronym MχD was introduced for this phenomenon. The first experimental evidence for the predicted MχD has been reported in 133 Ce [26], and also possibly in 107 Ag [27].It is also interesting to study the robustness of chiral geometry against the increase of the intrinsic excitation energy, i.e. if the chiral geometry is sustained in the higher-lying bands of a certain chiral configuration. In all the known cases the chiral doublet corresponds to the two lowest-lying bands of a configuration. Even for MχD in133 Ce [26] and 107 Ag [27], each chiral doublet structure corresponds to two lowest-lying bands with a distinct configuration. Therefore, study of the third and forth bands of the same chiral configuration is needed to answer the question of the investigated robustness. Very recent ...

The simple, longitudinal, and transverse wobblers are systematically studied within the framework of collective Hamiltonian, where the collective potential and mass parameter included are obtained based on the tilted axis cranking approach. Solving the collective Hamiltonian by diagonalization, the energies and the wave functions of the wobbling states are obtained. The obtained results are compared with those by harmonic approximation formula and particle rotor model. The wobbling energies calculated by the collective Hamiltonian are closer to the exact solutions by particle rotor model than harmonic approximation formula. It is confirmed that the wobbling frequency increases with the rotational frequency in simple and longitudinal wobbling motions while decreases in transverse wobbling motion. These variation trends are related to the stiffness of the collective potential in the collective Hamiltonian.

The lowest six rotational bands have been studied in the particle-rotor model with the particlehole configuration πh and different triaxiality parameter γ. Both constant and spindependent variable moments of inertial (CMI and VMI) are introduced. The energy spectra, electromagnetic transition probabilities, angular momentum components and K-distribution have been examined. It is shown that, besides the band 1 and band 2, the predicted band 3 and band 4 in the calculations of both CMI and VMI for atomic nuclei with γ = 30• could be interpreted as chiral doublet bands.PACS numbers: 21.60. Ev, 21.10.Re, 23.20.Lv Chirality is a subject of general interest in molecular physics, elementary particle physics, and optical physics. In atomic nuclear physics, the occurrence of chirality was originally suggested in 1997 by Frauendorf and Meng in the particle-rotor model (PRM) and tilted axis cranking (TAC) approach for triaxially deformed nuclei [1]. The predicted patterns of spectra exhibiting chirality were experimentally observed in 2001 [2]. Since then, the investigation of chiral symmetry in atomic nuclei has become one of the most hot topics in nuclear physics. Hitherto, more than 20 candidate chiral doublet bands in oddodd nuclei are proposed in the A ∼ 100, A ∼ 130, and A ∼ 190 mass regions. In addition, a few more candidates with more than one valence particle and hole were also reported in odd-A and even-even nuclei. For a review, see e.g. [3]. Even though there are many candidate chiral nuclei, the interpretation of the observed pair of near degenerate ∆I = 1 bands with the same parity as the chiral doublet bands is still an open question, accompanied with several competitive mechanisms [4].On the theoretical side, chiral doublet bands were first predicted by particle-rotor model (PRM) and tilted axis cranking (TAC) model for triaxially deformed nuclei [1]. Later on, numerous efforts have been devoted to the development of TAC methods [5][6][7] and PRM models [8][9][10][11] to describe chiral rotation in atomic nuclei. The characters of chiral doublet bands have been examined [12][13][14][15][16]. Recently, the PRM has been extended to the case of many particles and/or holes couples to a triaxially deformed core [17] that allows for the study of more general * Electronic address: jmyao@swu.edu.cn chiral rotating nuclei. As the counterpart, the interacting boson-fermion-fermion model has also been used to study the chiral doublet bands [18,19].In Ref.[20], the possible existence of multi-chiral doublet bands (MχD) in a single-nucleus 106 Rh has been proposed based on the triaxial relativistic mean-field calculations and been confirmed later in the similar calculations but with time-odd components [21]. Several minima with large triaxial deformation but with different high-j proton-particle and neutron-hole configurations, which are favorable for nuclear chirality, were found in the calculated potential energy surfaces of the rhodium isotopes 104,106,108,110 Rh [22]. In comparison with the MχD that differ from e...

A particle rotor model, which couples nucleons in four single-j shells to a triaxial rotor core, is developed to investigate the five pairs of nearly degenerate doublet bands recently reported in the even-even nucleus 136 Nd. The experimental energy spectra and available B(M 1)/B(E2) values are successfully reproduced. The angular momentum geometries of the valence nucleons and the core support the chiral rotation interpretations not only for the previously reported chiral doublet, but also for the other four candidates. Hence, 136 Nd is the first even-even candidate nucleus in which the multiple chiral doublets exist. Five pairs of chiral doublet bands in a single nucleus is also a new record in the study of nuclear chirality. * Electronic address: mengj@pku.edu.cn