Sound Velocities at High Pressure: An Application of Laser Induced Phonon Spectroscopy

PI将在华盛顿大学组建一个实验室，用于在高压和高温下测量候选地幔矿物的声速。在初步实验成功的基础上，他证明了在金刚石砧高压槽中对小（100微米）样品进行这种测量是可行的。激光诱导声子光谱形式的脉冲激发散射（ISS）为研究高压下晶体的弹性特性提供了一种可靠的技术。相干声子由一对重叠的激光脉冲产生，在时间和空间上调制样品的折射率。探测激光脉冲可以被由此产生的时间相关光栅强烈衍射。信号比任何其他技术都要大几个数量级。这种技术还避开了布里渊散射实验中经常出现的折射率不确定问题。在地幔条件下确定候选地幔组分弹性常数的压力和温度导数是当前矿物物理学中的重要问题之一。

The PI will assemble a laboratory at the University of Washington for the purpose of measuring sound velocities of candidate mantle minerals at high pressure and temperature. On the basis of successful preliminary experiments, he has demonstrated that it is feasible to make such measurements on small (100 um) samples in a diamond anvil high pressure cell. Impulsive stimulated scattering (ISS) in the form of laser induced phonon spectroscopy provides a robust technique to investigate the elastic properties of crystals at high pressure. Coherent phonons, generated by a pair of overlapping laser pulses, temporally and spatially modulate the index of refraction of sample. A probe laser pulse can be strongly diffracted by the resultant time-dependent grating. Signals are orders of magnitude greater than with any other technique. This technique also side-steps the uncertain index-of-refraction problem often associated with Brillouin scattering experiments. The determination, under mantle conditions, of pressure and temperature derivatives of elastic constants for candidate mantle constituents is one of the important current problems in mineral physics.