The study of fusion reactions at extreme sub-barrier energies has seen an increased interest in recent years, although difficult to measure due to their very small cross sections. Such reactions are extremely important for our understanding of the production of heavy elements in various environments. In this article, the status of the field is reviewed covering the experimental techniques, the available data, and the theoretical approaches used to describe such reactions. The fusion hindrance effect, first discovered in medium-mass systems, has been found to be relevant also for lighter systems. In some light systems, resonance structures are found to be important, while for heavy systems, the fission process plays an important role. In the near barrier region, couplings to collective excitations in the fusion participants and transfer reactions have been found to give a good description of the measured fusion cross sections and it results in a distribution of fusion barrier heights. New physics ingredients, related to the overlap process of the two projectiles, have to be introduced to describe the hindrance behavior. In addition, it has recently been found that the fusion cross section in both near-barrier and sub-barrier regions can be described very well in many cases using simple, analytical forms of the barrier-height distributions or a modified version of the classic Wong formula.

近年来，对极端子势垒能量下聚变反应的研究越来越受到关注，尽管由于它们的横截面非常小而难以测量。这种反应对于我们理解各种环境中重元素的产生极为重要。本文回顾了该领域的现状，包括实验技术、可用数据和用于描述此类反应的理论方法。聚变阻碍效应首先在中等质量的系统中发现，现已发现也与较轻的系统相关。在一些轻系统中，共振结构被发现很重要，而对于重系统，裂变过程起着重要作用。在近势垒区，已发现与聚变参与者中的集体激发和转移反应的耦合可以很好地描述测量的聚变横截面，并导致聚变势垒高度的分布。必须引入与两个射弹的重叠过程相关的新物理成分来描述阻碍行为。此外，最近发现，在许多情况下，使用势垒高度分布的简单分析形式或经典 Wong 的修改版本，可以很好地描述近势垒区和亚势垒区的融合截面。公式。必须引入来描述阻碍行为。此外，最近发现，在许多情况下，使用势垒高度分布的简单分析形式或经典 Wong 的修改版本，可以很好地描述近势垒区和亚势垒区的融合截面。公式。必须引入来描述阻碍行为。此外，最近发现，在许多情况下，使用势垒高度分布的简单分析形式或经典 Wong 的修改版本，可以很好地描述近势垒区和亚势垒区的融合截面。公式。