The spin and orbital contributions to magnetic dipole transitions

In previous works, we examined the systematics of magnetic dipole transitions in a single j shell. We here extend the study to large space calculations. We consider the nuclei [Formula: see text]Ti, [Formula: see text]Ti and [Formula: see text]Cr. Of particular interest are the contributions to [Formula: see text] of the spin and orbital parts of the magnetic dipole operator. Whereas usual scissors mode analyses have as an initial state the [Formula: see text] ground state (of an even-even nucleus), we here start with the lowest [Formula: see text] state. This enables us to reach many more states, e.g., [Formula: see text] 1, and 2 and thus get a better picture of the collectivity of this state.

Nuclear spin scissors mode – experimental status

A new type of nuclear collective motion - the spin scissors mode - was predicted seven years ago. Promising signs of its existence in 232Th were found. We perform a systematic analysis of experimental data on M1 excitations in rare-earth nuclei to find traces of the spin scissors mode in this area. Obvious signs of its existence are demonstrated.

Explanation of the puzzle of 164Dy scissors

The solution of TDHFB equations by Wigner Function Moments method with the isovectorisoscalar coupling taken into account leads to the prediction of the new type of nuclear spin scissors mode. It turns out that the lower group of M1 excitations in 164Dy, which is usually not included in the systematics of the scissors mode, can be quite naturally attributed to this new type of scissors.

Nuclear structure of 82Kr and 82Se relevant for neutrinoless double-beta decay

Nuclear Resonance Fluorescence (NRF) experiments on the nuclei 82Kr and 82Se were performed, that are a candidates for a mother-daughter pair for the hypothetical neutrinoless double-beta (0νββ) decay. The experiment aimed at providing high-precision data to benchmark theoretical calculations of the nuclear matrix elements involved in this exotic decay mode. We have investigated the excitation energy range from 2.3MeV to 4.2MeV, where the nuclear scissors mode is expected to be located in nuclei of this mass region. Our experiment was able to constrain decay branches of the scissors mode down to a level of a few percents, comparable to previous experiments on heavy deformed 0νββ decay candidates. Reduced transition strengths of the magnetic dipole-excited states have been determined by a method that exploits the non-resonant background in the NRF spectra. They are compared to a calculation within the nuclear shell model for 82Se, which reveals their mixed orbital and spin character, hinting at a more complex microscopic structure of low-lying 1+ states.