First proof-of-principle experiment with the post-accelerated isotope separator on-line beam at BRIF:measurement of the angular distribution of ^(23)Na+^(40)Ca elastic scattering

The reaction dynamics of exotic nuclei near the drip line is one of the main research topics of current interest.Elastic scattering is a useful probe for investigating the size and surface diffuseness of exotic nuclei.The development of rare isotope accelerators offers opportunities for such studies.To date,many relevant measurements have been performed at accelerators using the projectile fragmentation technique,while the measurements at accelerators using isotope separator on-line(ISOL)systems are still quite scarce.In this work,we present the first proof-of-principle experiment with a post-accelerated ISOL beam at the Beijing Radioactive Ion Beam Facility(BRIF)by measuring the angular distribution of elastic scattering for the stable nucleus^(23)Na from the doubly magic nucleus^(40)Ca at energies above the Coulomb barrier.The angular distribution measured by a silicon strip detector array in a scattering chamber using the ISOL beam at BRIF is in good agreement with that measured by the high-precision Q3 D magnetic spectrograph using the nonISOL beam at nearly the same energy.This work provides useful background for making BRIF a powerful tool for the investigation of the reaction dynamics of exotic nuclei.

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.

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.