Isospin effect on pre-scission γ emission

The influence of isospin on pre-scission giant dipole resonance (GDR) γ decay for nuclei 194Pb, 200Pb, 206Pb and 200Os is explored via a Langevin equation coupled with a statistical model. It is demonstrated that with increasing the isospin of these fissioning nuclei the sensitivity of the emitted γ multiplicity to the nuclear viscosity coefficient is decreased significantly. For 200Os nucleus, this γ-ray emission is no longer sensitive to the magnitude of the viscosity coefficient. In addition, isospin effect on the γ rays as a probe of nuclear dissipation is reduced with increasing angular momentum. These results suggest that to obtain a more accurate information of the viscosity coefficient by the measurement of pre-scission GDR γ-ray multiplicity it had better choose those compound systems with small isospin and low spin.