Nuclear Laser Spectroscopy of Be Isotopes with Ion-trap

该研究项目旨在开发一种实验方法来进行不稳定Be同位素的核激光光谱学。原子超精细相互作用中的超精细耦合常数A表现出弱但有限的同位素依赖性，称为超精细异常，其主要部分源于原子核中磁化强度分布的有限尺寸（Bohr-Weisskopf效应）。这种效应提供了一个独特的和有趣的探针的价中子在核中的分布，特别是在一个所谓的中子晕核，如Be-II。各种发展的实验技术已经进行了使用的稳定同位素Be-9被困在一个线性的RE陷阱放置在一个弱磁场。采用连续照射的方法，连续施加激光和微波辐射，证明了微波共振的高灵敏度检测。在几秒钟的测量中观察到高S/N共振信号。还使用脉冲方法测试了高精度测量。通过重复激光和微波交替照射的短周期（几ins），获得了相当高的2 × 1 O ~（-7）的准确度。对Be ~（-7）的第一不稳定同位素进行了实验研究，但至今没有观察到荧光信号。困难被认为是由于知识的运气在共振波长和事实上，在陷阱中的Be-7离子的数量是关键的。对于Be-11等寿命较短的同位素，利用RE离子导向技术，可以在线捕获碎片同位素分离器中的高能束流。

This research project aimed at developing an experimental method to perform nuclear laser spectroscopy of unstable Be isotopes. The hyperfine coupling constant A in the atomic hyperfine interaction shows a weak but finite isotope dependence called hyperfine anomaly, the main part of which stems from the finite size of the magnetization distribution in the nucleus (Bohr-Weisskopf effect). This effect affords a unique and interesting probe for valence neutron distribution in a nucleus, particularly in a so-called neutron halo nucleus such as Be-ll.Various developments for the experimental technique have been carried out using the stable isotope of Be-9 trapped in a linear RE trap placed at a weak magnetic field. High sensitive detection of microwave-resonance was demonstrated using continuous irradiation method where laser and microwave radiations were continuously applied. A high S/N resonance signal was observed with in a few seconds of measurement. A high precision measurement was also tested using a pulsed method. By repeating the short cycle (a few ins) of alternative irradiation of laser and microwave radiation, reasonably high accuracy of 2*1O-7 was obtained.Trial experiments for investigating the first unstable isotope of Be-7 have been carried out, however, no fluorescence signal was observed so far. The difficulty is considered to be due to the luck of knowledge in the resonant wave-length and to the fact that the number of Be-7 ions in the trap are critical. Various kind of improvements in the theoretical calculation of the specific isotope shift as well as in the experimental technique to increase the density of Be-7 ions in the trap are under progress.For shorter lifetime isotopes, such as Be-ll, an on-line trapping method for energetic beams from a fragment isotope separator is also under development using a newly proposed RE-ionguide technique.