Yang Sun

The Chern theorem is applied to intrinsically deformed atomic nuclei, leading to states exhibiting topological quantization of the rotation-aligned component of angular momentum averaged over Hilbert space. These topologically quantized alignment (TQA) states can emerge when collective rotation breaks intrinsic-frame time reversal symmetry, and differ fundamentally from traditional nuclear states. They exhibit formal analogies with the integer quantum Hall effect, and are a first suggestion that topological matter with novel properties might exist in nuclei. We discuss experimental signatures and speculate that TQA bulk-boundary correspondence could lead to a nuclear Chern insulator, where a rotating nucleus has an insulating bulk and unidirectional charged and uncharged currents at its surface, with detectable consequences for the energy spectrum.

High-spin states in the 68 165 , 166 , 167 Er nuclei were populated in the incomplete fusion of 55-MeV Li 7 ions with a Dy 164 target. Previously known rotational sequences in Er 165 , 166 , 167 have been extended, in some cases beyond the i 13 / 2 two-quasineutron crossing region. In Er 165 , four rotational sequences were observed up to a maximum I π of ( 45 / 2 + ); in Er 166 , five decay sequences were observed to I π = ( 28 + ); and in Er 167 , four decay sequences were populated to I π = ( 53 / 2 − ). Comparisons of the experimental data with the results of Cranked Shell Model calculations provide insight into the configuration dependence of the first two-quasineutron crossing frequencies and the blocking effects of the odd quasineutron in Er 165 and Er 167 . The experimental high-spin decay sequences in Er 165 and Er 167 have also been compared with the results of Projected Shell Model (PSM) calculations; the overall agreement between experiment and theory is very good over the complete range of spins for all high-spin rotational sequences. In particular, the observed signature splitting in the 5 / 2 + [ 642 ] band in Er 165 and in the 7 / 2 + [ 633 ] and 1 / 2 − [ 521 ] bands in Er 167 together with the absence of signature splitting in the high- K 11 / 2 − [ 505 ] band in Er 165 are reproduced in the PSM calculations. For Er 166 , the Triaxial Projected Shell Model calculations yield satisfactory results for both the ground and γ -vibrational band. For the latter band, there is a one-to-one correspondence between the theoretical results and experimental data for all states with I π in the range from the 2 + bandhead to the 21 + state.

Incorporating microscopic nuclear-structure information into the discussion of bulk properties of astronomical objects such as neutron stars has always been a challenging issue in interdisciplinary nuclear astrophysics. Using the rp-process nucleosynthesis as an example, we studied the effective stellar β^{+} and electron capture (EC) rates as well as the corresponding neutrino energy-loss rates of eight waiting-point (WP) nuclei with realistic stellar conditions and presence of strong magnetic fields. The relevant nuclear transition strengths are provided by the projected shell model. We have found that, on average, due to the magnetic field effect, the stellar weak rates can increase by more than an order of magnitude for all combinations of density and temperature, as well as in each of the WPs studied. We relate the onset field strength, at which the weak rates begin to increase, to nuclear structure quantities, Q value or electronic chemical potential μ_{e}. The enhanced weak rates may change considerably over the lifetime of WPs, thereby modifying the current understanding of the rp process.