Study of quantum fluid by structures in Raman spectra

本研究的目的是通过激光拉曼光谱的观测来验证超流氦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，数据的统计精度不够精确，无法详细讨论函数形式。因此，我们研制了多通道光谱仪，并成功地显著提高了精度。利用该光谱仪，我们重新确定了1.3 K饱和蒸汽压下超流氦的光谱结构。接下来，我们通过控制压力为1、3、5、6、10、15和20 kg/ <cm^2>来测量光谱的压力依赖性。光谱特征为<p_1>和<p_3>三个峰。在<p_1>和<p_2>之间的能量转移区观察到精细结构。主要发现了三个新的方面：1)<p_2>在压力为5kg / <cm^2>附近分裂为两个峰；2)<p_3>，新的…3)在10 kg/ <cm^2>的压力下，可以清晰地看到精细结构。精细结构的光谱形状不能用目前提出的理论来解释。我们进一步扩展了双转子峰<p_1>的测量，精度更高。峰值位置显示出不同于由中子散射确定的双转子能量的压力依赖性。我们将实验光谱形状与目前认为正确的理论模型计算结果进行了比较，选择峰位置和谱宽作为可调参数。我们发现它们之间存在不可忽视的差异。在峰的高能量侧，观察到精细的结构。这种结构对施加的压力有敏感的依赖性。考虑到上述新方面，我们认为光谱结构是阐明超流氦4微观凝析态的有力工具。少

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