Gamma-ray spectroscopy of neutron-rich A~100nuclei

壳层模型是描述原子核结构的最著名的模型之一。它类似于原子壳层模型，因为质子和中子都有自己独立的壳层，当这些壳层被填满时，通过降低每个核子的结合能，为原子核提供更大的稳定性。这些壳层以特定的数量出现，但已被证明与电子的原子壳层模型不同。这个模型的一个问题是，它使计算每个核子的束缚能变得困难，要做到这一点，必须计算每个核子之间的相互作用，这对于重核来说变得特别困难，因此必须应用其他方法（国家研究委员会，1999）。液滴模型对于核子结合能的预测非常准确，误差很小（Moller, et al., 1984）。它将原子核比作液滴，以及液体中的分子如何与原子核中的核子相互作用，因为两者都具有均匀的密度，并且在相互作用时表现出相似的特征。这方面的例子是，核裂变可以被认为是分子的分裂，粒子的衰变类似于蒸发的发射，辐射的发射类似于冷却（Brehm和Mullin， 1989）。这些模型，连同其他各种模型，都增加了我们对原子核结构的理解，并重现了已经测量过的质量。然而，仍有大量的原子核尚未被实验测量，特别是对于富含中子的原子核，研究这些未知数对于发展我们对原子核的认识是必不可少的。有各种各样的方法来研究原子核的质量，其中一种是通过磁谱仪测量飞行时间，它可以用来找到质量，因为它与质量比的变化成正比。这方面的一个例子是GANIL，其中电荷与质量比相似的原子核在回旋加速器内加速，由于较轻的原子核比较轻的原子核加速得更快，因此到达探测器时会有延迟。这个时间延迟可以用来计算原子核的电荷质量比，精度很高（Chartier, 2002）。

The shell model is one of the most well-known models for describing the structure of the nucleus. It is similar to the atomic shell model as protons and neutrons have their own independent shells which when filled offer greater stability for the nucleus by having a reduced binding energy per nucleon. These shells occur at specific numbers however have been shown to be different to atomic shell model for electrons. A problem with this model is that it makes calculating the binging energy per nucleon difficult as to do this the interaction between each of the nucleons must be calculated which becomes exceptionally difficult for heavy nuclei, thus other methods must be applied (National research council, 1999).The Liquid drop model has been shown to be very accurate for predicting the binding energies of nucleons with very small error (Moller, et al., 1984). It compares the nucleus to a liquid droplet and how molecules in a liquid will interact with each other similar to the nucleons in a nucleus as both will have uniform density and exhibit similar characteristics when interacted with. Examples of this are that nuclear fission can be thought of as the splitting of a molecule, particle decay is similar to emission by evaporation and emission of radiation is similar to cooling (Brehm and Mullin, 1989).These models, along with various others, have all added to our understanding of the structure of nuclei and have reproduced masses that have already been measured. However there are still a large number of nuclei that have not yet been measured experimentally, particularly for neutron rich nuclei and investigating these unknowns is essential to developing our knowledge of the nucleus.There are various methods for investigating the mass of nuclei, one of which is the measurement of the time of flight through a magnetic spectrometer which can be used to find the mass as it is proportional to the change to mass ratio. An example of this is GANIL where nuclei of similar charge to mass ratios are accelerated within a cyclotron and as the lighter of the nuclei will accelerate faster than the lighter nuclei, there will be a delay in arrival at the detector. This time delay can then be used to calculate the charge to mass ratio of the nuclei to a high degree of accuracy (Chartier, 2002).