Fusion Hindrance Factor of Heavy Nuclei Extracted from Experimental Data

The reactions of ¹⁶O+²⁰⁴Pb, ⁸²Se+¹³⁸Ba and ⁹⁶Zr+¹²⁴Sn lead to the same compound nucleus ²²⁰Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted the fusion hindrance factor from the evaporation residue cross sections for the reactions of ⁸²Se+¹³⁸Ba and ⁹⁶Zr+¹²⁴Sn and compared with the results calculated using a two-parameter Smoluchowski equation. The theoretical predictions are basically in agreement with the experimental data. It is found that the probability of forming a compact ²²⁰Th is less than 10% for the reactions considered. For the systems more massive than ²²⁰Th, fusion should be much more strongly suppressed due to the competition of quasifission with complete fusion. Understanding of this inhibition is essential to forming new superheavy nuclei.