Discovery of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Na</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>39</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
D. S. Ahn, Jun Amano, H. Baba, N. Fukuda, H. Geissel, N. Inabe, Shinsuke Ishikawa, N. Iwasa, T. Komatsubara, T. Kubo, K. Kusaka, D. J. Morrissey, T. Nakamura, M. Ohtake, H. Otsu, Toshihiko Sakakibara, Y. Satou, B. M. Sherrill, Y. Shimizu, T. Sumikama, Hiroaki Suzuki, H. Takeda, O. Tarasov, H. Ueno, Y. Yanagisawa, K. Yoshida
Abstract
The new isotope ^{39}Na, the most neutron-rich sodium nucleus observed so far, was discovered at the RIKEN Nishina Center Radioactive Isotope Beam Factory using the projectile fragmentation of an intense ^{48}Ca beam at 345 MeV/nucleon on a beryllium target. Projectile fragments were separated and identified in flight with the large-acceptance two-stage separator BigRIPS. Nine ^{39}Na events have been unambiguously observed in this work and clearly establish the particle stability of ^{39}Na. Furthermore, the lack of observation of ^{35,36}Ne isotopes in this experiment significantly improves the overall confidence that ^{34}Ne is the neutron dripline nucleus of neon. These results provide new key information to understand nuclear binding and nuclear structure under extremely neutron-rich conditions. The newly established stability of ^{39}Na has a significant impact on nuclear models and theories predicting the neutron dripline and also provides a key to understanding the nuclear shell property of ^{39}Na at the neutron number N=28, which is normally a magic number.