A development of lifetime measurement based on the differential decay curve method

A new development of indirect gating case in the differential decay curve method used for lifetime measurement has been introduced.The gate region was extended from partial shifted peak to both shifted and unshifted components.The statistics of flight and stop peaks in gating spectra was improved obviously.The reliability of this change has been tested by reanalysing the lifetime of 2^+ state in^(134) Ce.The result of 32.2(33) ps was fit well with the previous published values within the experimental uncertainty.The developed method was also used to analyse the lifetime of 2_1^+ state in^(138) Nd.

Lifetime measurements in 138Nd

Lifetimes of the 2_(1)^(+),4_(1)^(+),7_(2)^(-),10_(2)^(+),12_(2)^(+),and 14_(1)^(+) states in 138 Nd populated via the 123 Sb(19 F,4n)138 Nd fusion–evaporation reaction were measured with the recoil distance Doppler shift technique in combination with the differential decay curve method.The B(E2;2_(1)^(+)→0_(1)^(+))value fit well with the systematic trend in the Nd isotope chain and Grodzins rule,which proved that 138Nd is a transitional nucleus.

Core breaking and possible magnetic rotation in the semimagic nucleus ^(90)Zr

The semimagic nucleus^(90)Zr,with Z=40 and N=50,is investigated in terms of large scale shell model calculations.A logical agreement is obtained between the available experimental data and predicted values.The calculated results indicate that the low-lying states are primarily dominated by the proton excitations from the fp orbitals across the Z=38 or 40 sub shell into the high-j 1g_(9/2)orbital.For the higher-spin states of^(90)Zr,the breaking of the N=50 core plays a crucial role,and the contribution of different orbitals to each state are discussed in this article.The evolution from neutron core excitations to proton excitations is systematically studied along the neighboring N=50 isotones.Furthermore,the strongΔI=1 sequence demonstrates an abrupt backbend attributed to the alignment of the valence nucleons in fp proton orbitals and is proposed to have aπ(fp)^(-2)(1g_(9/2))^(2)■v(1g_(9/2))^(-1)(2d_(5/2)/1g_(7/2))^(1)configuration before the backbend,based on the shell model calculations.The properties of this sequence before the backbend indicate a general agreement with the fingerprints of magnetic rotation;hence,the sequence with theπ(fp)^(-2)(1g_(9/2))^(2)■v(1g_(9/2))^(-1)(2d_(5/2)/1g_(7/2))^(1) configuration is suggested as a magnetic rotational band arising from shears mechanism.

Possible multiple antimagnetic rotational bands in odd-A^(103,105)Pd and^(109)Cd nuclei

The positive-parity signature partner bands in^(103,105)Pd and^(109)Cd nuclei are investigated using the classical particle-rotor model.Based on the systematic study of neighbouring nuclei,the signature partner bands of ^(105)Pd are assigned to theπ(g^(-4)_(9/2))■ν(g7/2h^(2)_(11/2))configuration,and this assignment is also supported by the present calculations.Furthermore,the calculated$B(E2)$values of such bands of ^(105)Pd reproduce the experimental values well and exhibit a decrease with increasing angular momentum,suggesting that these two bands may originate from antimagnetic rotation.Similar signature partner bands are also found in the neighboring^(103)Pd and^(109)Cd nuclei.The properties of both bands are in general agreement with the fingerprints of antimagnetic rotation,and thus the signature partner bands of^(103)Pd and^(109)Cd are suggested to be candidates for the multiple antimagnetic rotational bands of ^(105)Pd.In addition,the evolution of the two-shears-like mechanism for possible multiple antimagnetic rotational bands in^(103,105)Pd and^(109)Cd nuclei is examined by investigating the orientation of the angular momenta.

Multi-quasiparticle excitations and the impact of the high-j intruder orbital in the N=51^93 Mo nucleus

The level structures of 93 Mo are investigated using Large Scale Shell Model calculations,and reasonable agreement is obtained between the experimental and calculated values.The calculated results show that the lower-lying states are mainly dominated by proton excitations from the If5/2,2 p3/2,and 2 p1/2 orbitals into the higher orbitals across the Z=38 or Z=40 subshell closure.For the higher-spin states,multi-particle excitations,including the excitation of 2 d5/2 neutrons across the N=56 subshell closure into the high-j intruder 1 h11/2 orbital,are essential.Moreover,the previously unknown spin-parity assignments of the six higher excited states in 93 Mo are inferred from the shell model calculations.

Low-lying states of 92,93Nb excited in the reactions induced by the weakly-bound nucleus 6Li near the Coulomb barrier

Excited states of odd-odd nucleus 92Nb and odd-A nucleus 93Nb were populated in the 6Li+ 89Y reaction with an incident energy of 34 MeV. The processes that produce 92,93Nb and can be measured by a combination of light charged particle and gamma ray measurements are discussed. Twenty new transitions are observed and eight new levels are constructed in 92Nb, and in addition two new transitions are added to the level scheme of 93Nb. Using shell model calculations, the low-lying structure of 92Nb is investigated and compared with the experimental results.

Lifetime measurement for the 2^+1 state in^106Cd

The lifetime of the 2^+1 state in ^106Cd populated via the ^94Zr(^16O,4n)^106Cd reaction has been measured with the Recoil Distance Doppler Shift technique in combination with the Differential Decay Curve Method.By subtracting the contamination in the data,the mean lifetime of the I^π=2^+1633 keV state was determined as 9.9(12)ps.The B(E2)value calculated in this study is in good agreement with the experimental systematics and was compared to the shell model calculations.