Discovery of Ca60 and Implications For the Stability of Ca70

Abstract

The discovery of the important neutron-rich nucleus _{20}^{60}Ca_{40} and seven others near the limits of nuclear stability is reported from the fragmentation of a 345 MeV/u ^{70}Zn projectile beam on ^{9}Be targets at the radioactive ion-beam factory of the RIKEN Nishina Center. The produced fragments were analyzed and unambiguously identified using the BigRIPS two-stage in-flight separator. The eight new neutron-rich nuclei discovered, ^{47}P, ^{49}S, ^{52}Cl, ^{54}Ar, ^{57}K, ^{59,60}Ca, and ^{62}Sc, are the most neutron-rich isotopes of the respective elements. In addition, one event consistent with ^{59}K was registered. The results are compared with the drip lines predicted by a variety of mass models and it is found that the models in best agreement with the observed limits of existence in the explored region tend to predict the even-mass Ca isotopes to be bound out to at least ^{70}Ca.

Chiral g -matrix folding-model approach to reaction cross sections for scattering of Ca isotopes on a C target

“…As an important property of Ca isotopes, we first determined the odd and even driplines by seeing A dependence of S 1 and S 2 , and found that 64 Ca is an even-dripline nucleus and 59 Ca is an odd-dripline nucleus. As for E B in addition to S 1 , S 2 , our results agree with the experimental data [1][2][3][4] in 40−58 Ca. Our results are thus accurate enough for the prediction on the odd and even driplines.…”

“…Experimental data (crosses) are taken from Refs. [1][2][3]. The GHFB+AMP results are close to the GHFB ones (closed circles) for even Ca isotopes; in fact, the former deviates from the latter at most by 0.73 %.…”

“…The odd and the even dripline are determined from mass-number (A) dependence of the one-neutron separation energy S 1 (A) ≡ E B (A) − E B (A − 1) and the two-neutron separation energy S 2 (A) ≡ E B (A) − E B (A − 2); see Refs. [1][2][3][4] for the experimental data.…”

Soft breathing modes in neutron-rich nuclei with the subtracted second random-phase approximation

“…4 for this peak. It may be seen that the physical nature of this excitation mode has strongly evolved compared to the case of 40 Ca. Now this excitation is mainly driven by neutrons.…”

“…In Sec. III we consider the case of the N = 20 N = Z nucleus 40 Ca to check whether a low-lying monopole excitation is predicted for this nucleus (having no neutron excess) and which is its nature. In the same section, more neutron-rich Ca isotopes are analyzed, 48 Ca (δ = (N − Z)/A = 0.17) and 60 Ca (δ = 0.33), and the evolution of the physical nature of the predicted low-lying strength is investigated going from N = 20 to N = 28.…”