- (156) Of Tm Nuclear High Spin States Of Experimental Research

Nuclei in the mass A¹50 region exhibit strongly competition between the collective andsingle particle characters. The structure will change largely when the nucleon number increasesor reduces. ¹⁵⁶Tm, far away from double magic nucleus, belongs to the rare-earth nuclei. Thehigh spin information of ¹⁵⁶Tm is rare . Nuclei with N 88 exhibit collective character whilewith N 86 exhibit single-particle character, and with N=87 exhibit characteristics of bothcollective and single-particle modes. So the study of ¹⁵⁶Tm is interesting for us to learn theevolution of the two shapes and the systematic of its isotones or isotopes. The experiment has been performed in the HI-13 tandem accelerator at the China Instituteof Atomic Energy. The high spin states of ¹⁵⁶ Tm have been populated via heavy-ion fusionevaporation reaction ¹⁴²Nd(¹⁹F, 6n) ¹⁵⁶Tm. The beam energy was 122.5MeV and the target wasa self-supporting foil with 2.2mg/cm² thickness. The -rays from the evaporated residues weredetected with an array consisting of thirteen Compton suppressed HPGe-BGO spectrometers.Single (?)-ray spectra were collected at beam energy from 110MeV to 125MeV for excitationfunction measurement. A (?)-(?) coincidence experiment was performed at beam energy of122.5MeV and beams current of 15nA. About 1.7×10⁸ coincident events with fold 2 werecollected during 100 hours beam time. Two matrixes were found, one was E(?)-E(?) symmetricalmatrix, the other was unsymmetrical matrix with X axis and Y axis located ±45°and±90°positions. From the coincidence analysis, more than 30 new -rays were identifiedbelonging to ¹⁵⁶Tm by gated on known -rays. And the new level scheme of ¹⁵⁶Tm wasestablished. This thesis mainly concerns the in-beam (?)-ray spectroscopic techniques and theirapplications in the study of high-spin level structures of N=87 ¹⁵⁶Tm nuclei.