Study of quantum fluid by structures in Raman spectra

本研究的目的是通过对激光拉曼光谱的观察，确定超流氦4的微观状态。在饱和蒸汽压下超流氦的拉曼光谱中发现了精细结构。然而，数据的统计准确性不够准确，无法详细讨论函数形式。为此，我们研制了一种多道光谱仪，并成功地显著提高了测量精度。利用这台光谱仪，我们重新确定了1.3K饱和蒸气压下超流氦的光谱结构。然后，通过控制压力分别为1，3，5，6，10，15和20 kg/&lt；cm^2&gt；测量了光谱的压力依赖关系。在&lt；p1&gt；和&lt；p2&gt；之间的能量移动区观察到了精细结构。主要发现了三个新的方面：1)在5 kg/&lt；cm；2)&lt；p_3&gt；的压力附近出现两个峰，新的…在这项工作中发现的更多，随着压力的增加而变得清晰。3)在高达10 kg/lt；cm^2的压力下，细小组织清晰可见。精细结构的光谱形状不能用目前提出的理论来解释。我们进一步扩展了对两个子峰的测量，提高了测量的精度。峰的位置与由中子散射确定的两子能量的压力关系不同。我们将实验光谱形状与目前认为正确的理论模型计算进行了比较，选择了峰位和光谱宽度作为可调参数。我们发现它们之间有不可忽视的差异。在峰的高能一侧，观察到了精细结构。已发现该结构敏感地依赖于所施加的压力。考虑到上述新的方面，我们计算光谱结构是阐明超流氦4微观凝聚态的有力工具。

The purpose of this research is to cralify the microscopic state of the superfluid helium 4 by the observation of laser Raman spectra. Fine structures have been found in the Raman spectra of the superfluid helium under saturated vapor pressure. However, the statistical accuracy of the data was not accurate enough to discuss the functional form in detail. Thus we developped a multi-channel spectrometer and succeeded in increasing accuracies remarkably. With this spectrometer, we re-confirmed the spectral structures of the superfluid helium under saturated vapor pressure at 1.3 K. Next, we measured the pressure dependence of the spectra by controlling the pressures to be 1,3,5,6,10,15, and 20 kg/ <cm^2> .The spectra are characterized by apprearance of three peaks <p_1> , and <p_3> . The fine structures are observed in the energy shift region between <p_1> and <p_2> . Mainly three new aspects have been found: 1) <p_2> splits into two peaks near the pressure of 5 kg/ <cm^2> .2) <p_3> , new … More ly found in this work, becomes clear as the pressure is increased. 3) The fine structures are clearly seen under the pressure up to 10 kg/ <cm^2> . The spectral shape of the fine structures cannot be explained by theories so far proposed. We further extended measurements of the two-roton peak <p_1> with higher accuracies. The peak position has been found to show a pressure dependence different from that of the two-roton energy determined by the neutron scattering. We made comparisons of the experimental spectral shapes with the theoretical model calculations so far believed to be correct, choosing the peak position and the spectral width as the adjustable parameters. We found non negligible discrepancies between them. In the higher energy side of the peak, fine structures are observed. The structure has been found to depend on the applied pressure sensitively. Considering above mentioned new aspects, we calim the spectral structures is a powerful tool to clarify the microscopic condensate state of superfluid helium 4. Less