High-spin isomer and level structure of 145Sm

Abstract

A high-spin isomer in 145 Sm was discovered by using Inverse kinematic reactions, 20 Ne e Xe,a7n) 145 Sm and 16 0 e 36 Xe,7n) 145 Sm. The half life was determined to be 0.96 J.LSec. Sixty-five 1-rays were identified by the /')'-coincidence measurements to belong to the isomer decay. The low-lying level scheme of 145 Sm was established in detail by the in-beam 1-ray measurements using the 139 La e 0 B,4n) 145 Sm reaction. A complex decay scheme of this isomer was constructed by using the data obtained from the 136 Xe induced reactions, combining the informations of low-lying states mentioned above. The excitation energy of this isomer was determined to be 8.8 MeV. The /')'-coincidence measurement using the 138 Ba (13 C,6n) 145 Sm reaction was also performed. Based on this information, the level scheme above the high-spin isomer was extended up to the state at 14.6 MeV. A 1-ray angular distribution measurement using the same reaction with pulsed beam was carried out and was used to assign a spin value of each level. Low-lying states in 145 Sm were interpreted to originate from a single neutron coupled to the 144 Sm core excitation. Experimental yrast states were compared with a calculation of a deformed independent particle model (DIPM). A configuration of the high-spin isomer was deduced by the DIPM calculation to be { 7r h ll /2 2 v (f 7 /2 h 9/2 i 13/2) } 49/2+ .

Possibility of shears mechanism due to attractive interaction in the island of $A$ $\sim$ 140 region

“…Above the 29/2 (+) 4389-keV excited state of the 145 Sm, a dipole band-like structure having M1 γ transitions of energies 715, 477, 397 and 313-keV was observed by the A. Odahara et al [17] (Fig. 6 (a)).…”

“…This is due to the fact that here, neutron(s) is(are) outside the N = 82 core and protons can be easily excited to the h 11/2 orbital from the g 7/2 /d 5/2 orbital make them to realize as particle character. In reality, the excitation spectra of the 145 Sm [17] and 146 Eu [18] nuclei exhibit the band-like structure consisting of the strong M1 transitions having decreasing gamma energy with spin.…”

“…The emphasis will be given to explore the possibility of the attractive shears (shears blades are produced by the similar type of the valence particles i.e either particles or holes) of these nuclei as hinted by Clark and Macchiavelli. The possible candidature of the attractive shears for the N = 83 145 Sm [17] and 146 Eu [18] isotones will be discussed.…”

“…7: (Color online)The partial level scheme of the (a)145 Sm and (b)146 Eu nuclei showing the possible candidate of the attractive shears bands. The level scheme are adopted from the Refs [17,18]…”

Gamma-ray and conversion-electron spectroscopy of the high-spin isomer in 145Sm

“…Among the N = 83 isotones, high-spin isomers have been reported at ≈9-MeV excitation energy in 143 Nd [1], 144 Pm [2], 145 Sm [3], 146 Eu [4], 147 Gd [5], 148 Tb [6],…”