Investigation of the low-energy dipole response in transfermium nuclei: The case of 250,252,254,256No

Up to now the dipole excitation of many nuclei have been investigated and discussed through both theoretical and experimental studies in the spectroscopic energy region. However, questions remain regarding the dipole response of heavy deformed nuclei such as transfermium. In this study, the electric dipole (E1) and magnetic dipole (M1) response for the transfermium [Formula: see text]No nuclei in the spectroscopic energy region within the framework of the rotational and transitional invariant QRPA model were investigated. Where, the predicted concentration of the M1 states to the summed dipole strength was found to be 65–67%, with E1 states contributing the remaining 33–35% to this region. These showed, the E1 strength makes a noticeable impact on spectroscopic region in No isotopes. The calculations reveal that M1 excitations are mainly observed up to 2.7[Formula: see text]MeV, centered around [Formula: see text][Formula: see text]MeV, whereas the E1 excitations are concentrated around 2[Formula: see text]MeV and above 3.5[Formula: see text]MeV. This provides a possible interpretation of the experimentally observed dipole excitations with unknown parity in these regions. The obtained results are in good agreement with the available experimental data.