Researchers at Institute of Modern Physics, Chinese Academy of Sciences (IMP) have experimentally explored the high-spin level structure of the doubly odd nucleus ¹⁰⁴Ag by means of in-beam γ-ray spectroscopy techniques.  

Particle-hole nuclei around the doubly magic nucleus ¹⁰⁰Sn exhibit the coexistence of single-particle and collective-rotational structure. The collective rotation is traditionally understood as the motion of the deformed nucleus. However, during the past two decades, lively research has sprung up in the magnetic rotational band and the chiral doublet bands. The magnetic rotational band can be generated by the alignment of the h_11/2 neutron-particle and g_9/2 proton-hole in the A » 100 mass region. ¹⁰⁴Ag has three high-j proton holes and seven neutron particles outside the ¹⁰⁰Sn core. It is expected that the single-particle excitation, magnetic-dipole and electric-quadrupole rotational structures, and nuclear chirality can coexist in this typical particle-hole nucleus.   

The experiment was performed at the HI-13 Tandem Accelerator Laboratory of the China Institute of Atomic Energy. High-spin states of ¹⁰⁴Ag were populated using the ⁹⁷Mo(¹¹B, 4n) reaction at an incident beam energy of 50 MeV. A total of 1.5 ´ 10⁸ coincidence events were recorded using an array of 13 Compton-suppressed HPGe detectors. The present level scheme of ¹⁰⁴Ag has been established based on the experimental results.   

Besides those reported in previous works, more than 40 new γ rays are observed in this experiment. Two positive-parity bands associated with the pg^-1_9/2Änd_5/2 and pg^-1_9/2Äng_7/2 configurations are extended significantly. Based on the comparison with the features of nuclear chirality, the negative parity bands are suggested as candidate chiral doublet bands with the pg^-1_9/2Änh_11/2 configuration.  

In previous literatures, the lower-lying levels of ¹⁰⁴Ag were assigned to have the single-particle nature and the positive-parity band F as a magnetic rotational band. Therefore, the odd-odd nucleus ¹⁰⁴Ag has exhibited the coexistence of single-particle and collective-rotational structure.  

The results have been published in Phys. Rev. C88, 024306 (2013). 

Fig.1 Level scheme of ¹⁰⁴Ag deduced from the present work. (Image by IMP)