Detection of Quantum Properties of Liquid Helium by use of Atoms and Molecules as Optical Probes

本文从理论和实验两方面研究了注入液态氦-3和氦-4中的Ca原子的光谱。相对于氦-4，较小的原子质量导致氦-3的液体密度较低。氦-3作为费米子原子的统计特性使得氦-3的表面张力比玻色子氦-4小。我们基于气泡理论的模型计算表明，液氦的这些量子力学和统计特性在这些光谱中表现为液体同位素之间光谱位移和宽度的巨大差异。研究了氦-3和氦-4加压液态中Mg原子的发射和激发光谱。Mg原子的发射光谱几乎不依赖于压力，这与迄今为止观测到的其他原子的发射光谱随压力向蓝边偏移并变宽形成了对比。理论研究表明，液态氦中Mg原子的这种光谱特征可以用Mg- he_n的激复模型来解释。在冷氦气中观测到Bay的发射光谱是氦压力和温度的函数。基于速率方程的分析揭示了Ba^+He：的形成、解离和振动弛豫等碰撞动力学。

Spectra of Ca atoms implanted in liquid helium-3 and helium-4 have been investigated both experimentally and theoretically. Smaller atomic mass leads to the lower density of liquid for helium-3 compared with helium-4. And the statistic character of helium-3 as fermionic atoms results in the smaller surface tension for liquid helium-3 compared with bosonic liquid helium-4. Our model calculation based on the bubble theory has shown that these quantum mechanical and statistic character of liquid helium are manifested in these spectra as large differences in the spectral shift and width between liquid isotopes.Emission and excitation spectra of Mg atoms in pressurized liquid helium-3 and helium-4 have been observed. Emission spectra of Mg atom have almost no dependence on the pressure, which is in contrast to the fact that emission spectra for the other atomic species observed so far shifts to blue side and broaden with the pressure. Theoretical investigations have indicated that this spectral feature of Mg atom in liquid helium can be explained by the exciplex model of Mg-He_n.Emission spectra of Bay in cold helium gas have been observed as a function of helium pressure and temperature. Analysis based on rate equations have revealed the collision dynamics such as the formation, dissociation and vibrational relaxation of Ba^+He:.