Studies of Anomalously Long-Lived Hadronic Atoms

本研究的目的是：1）使用欧洲核子研究中心（CERN）的LEAR装置对反质子氦原子进行精确的激光光谱学研究; 2）使用GSI（德国）的FRS光谱仪对深束缚的π原子进行研究。对于前者，我们在反质子氦-3和氦-4原子中发现了许多激光诱导共振，从而建立了对这些原子的结构和动力学的认识;而对于后者，我们首次成功地观察到2p和1s态的形成，在（d，1）在欧洲核子研究中心（CERN）低能反质子环（LEAR）上对反质子氦原子进行了高精度激光光谱测量。1996年，我们的重点是高精度测量共振轮廓。近年来，反质子氦能级结构理论计算的发展，使其共振波长的预测精度优于50ppm。此外，在理解和理解方面正在取得重大进展， ...更多信息 反质子氦的精细和超精细结构。使用高分辨率模式，我们成功地解决了一个超精细的双重结构，观察到的分裂与理论预测，使用高精度的相对论变分计算符合得很好。我们还发现共振波长、宽度和能级寿命与压强有显著的相关性。目前，我们采用LEAR的慢引出模式，在靶中一次接受一个反质子，用高功率激光辐照单个反质子氦原子。从1995年开始，我们开始发展一种新的技术--脉冲激光共振法。也就是说，在短时间内从LEAR中提取了超过1000万个反质子，并施加了一个激光脉冲来观察共振。这种方法被证明是一个非常强大的工具，找到弱共振线。2）在德国GSI的FRS谱仪上，首次在Pb-208靶上的（d，3He）反应中发现了深束缚的π原子。传统上，通过观察在去激发期间发射的X射线来进行π原子光谱学。但是，由于π波函数与原子核的重叠部分越大，在深束缚（1s，2p）态中也是如此，π吸收比X射线发射更频繁地发生，因此用常规方法无法获得深束缚态的信息。因此，我们开发了一种利用核反应在深束缚原子轨道中直接产生π的新方法。例如（n，d）或（d，3 He）。在1996年我们在GSI测量的（d，3He）谱中，由于2p和1s介子Pb原子的形成而产生的峰被清楚地看到。从峰的位置和峰的宽度，它将成为可能，以更好地了解π介子核相互作用。少

This research was aimed at 1) precise laser spectroscopy of antiprotonic helium atoms using the LEAR facility at CERN (Switzerland) and 2) search for deeply-bound pionic atoms using the FRS spectrometer at GSI (Germany). For the former we have discovered many laser-induced resonances in antiprotonic helium-3 and -4 atoms thus establishing knowledges on the structure and dynamics of these atoms, while for the latter we have succeeded in observing formation of 2p and 1s states for the first time, in the (d, 3He) reaction on Pb-208 target.1) High precision laser spectroscopy of antiprotonic helium atoms was performed at the CERN low energy antiproton ring (LEAR). In 1996, our emphasis was on the high-precision measurement of the resonance profile. Recent development in the theoretical calculation of antiprotonic helium level structure has made it possible to predict the resonance wavelengths in a better-than 50 ppm accuracy. In addition, a significant progress is being made in understandi … More ng the fine and hyperfine structure of antiprotonic helium. Using the high-resolution mode, we successfully resolved a hyperfine doublet structure, and the observed splitting was in good agreement with the theoretical prediction using a high-precision relativistic variational calculation. We also discovered a significant pressure dependence of the resonance wavelengths, widths and level lifetimes.So far, we used the slow-extraction mode of LEAR,and accepted one antiproton at a time in our target, and irradiated a single antiprotonic helium atom with a high power laser. From 1995, we started to develop a novel technique of pulsed-beam laser resonance method. Namely, more than 10 million antiprotons were extracted from LEAR in a short burst, and a single laser pulse was applied to observe the resonance. This method turned out to be a very powerful tool to find weak resonance lines. Seven new resonance lines were discovered using this new method.2) Deeply-bound pionic atoms were discovered for the first time in the (d, 3He) reaction on Pb-208 target, using the FRS spectrometer at GSI (Germany). Conventionally, pionic atoms spectroscopy was done by observing X-rays emitted during deexcitation. However, as the overlap between the pion wavefunction and the nucleus becomes larger, which is true for the deeply-bound (1s, 2p) states, the pion absorption occurs more frequently than X-ray emission, hence it is impossible to obtain information on the deeply-bound states in the conventional method.We therefore developed a new method of directly producing a pion in the deeply-bound atomic orbit using a nuclear reaction, such as (n, d) or (d, 3He). In the (d, 3He) spectrum we measured at GSI in 1996, the peaks due to the formation of 2p and 1s pionic Pb atoms were clearly seen. From the peak locations and the peak widths, it will become possible to better understand the pion-nucleus interaction. Less