The level states of the nucleus 124Cs have been populated through the 116Sn(11B,3n) reaction at a beam energy of 45 MeV, provided by the HI-13 tandem accelerator of the China Institute of Atomic Energy. A number of low-lying states are constructed. The level states in the πh11/2 ⊗vg7/2 side band are extended down to lower spin by one h. The level energies and spins in the rotational bands are determined through the establishment of various connections, which con rm the spin assignment of the yrast band in 124Cs based on excitation energy systematics. It is revealed that with the present spin assignment, the πh11/2 ⊗vg7/2 side band shows signature inversion at low-spin region and the inversion occurs at a spin of about 16h.

High spin states of 122Cs are reinvestigated through the 116Sn (10,B 4n) 122Cs reaction at the beam energy of 54 MeV. Two new levels are added to the lower side of the most strongly populated band and the previously proposed 488 keV linking transition between the two observed bands is replaced by the 95 keV linking transition. As a result of these newobservations, it becomes reasonable to assign the most strongly populated band in 122Cs as the πh11/2⊗vh11/2 yrast band.

High spin states of odd-odd nucleus 124Cs have been studied following the 116Sn(11B,3n) reaction at a beam energy of 45 MeV. The previously reported isolated rotational bands are connected to each other by various linking transitions and to the 11 ground state through different decay paths. The spin of the lowest observed state in the ph11/2⊗ vh11/2 yrast band is determined to be 9\, which is two units larger than that suggested by the latest in-beam study and confirms the spin assignment proposed by a recent systematics study on spin assignment and signature inversion of the ph11/2⊗ vh11/2 bands in odd-odd isotopes 118-132Cs.

The excitation energy systematics of ph11/2⊗n h11/2 yrast bands of odd-odd isotopes 118-132Cs are studied, and as a result of this study we suggest that the spin values of lowest observed states of yrast bands of 118,122,124,126,128Cs be reassigned as 8, 9, 9, 9, and 10, respectively. These new spin assignments are also supported by the argument of alignment additivity.

According to the argument of excitation energy systematics, new spin values are assigned to the lowest observed states of the ph11/2⊗n h11/2 bands for doubly odd nuclei 124,126,130,132,134La, 130-134Pr, 136,138Pm, and 138Eu, and possible new spin values are discussed for doubly odd nuclei 120-130Cs. Based on these new spin assignments, two systematic features of the ph11/2⊗n h11/2 bands are revealed. First, the low spin signature of the ph11/2⊗n h11/2 band is inverted for all doubly odd nuclei discussed in the present work. Second, the observed inversion spin increases with increasing neutron number for Cs and La isotopes. These features are in agreement with the recent systematic calculations based on the particle-triaxial-rotor model, with the inclusion of zero-range residual interaction between unpaired proton and neutron of Semmes and Ragnarsson, performed by Tajima.