It has been demonstrated for the first time that pulsed laser Raman spectroscopy can be used for diagnostics of a local acoustic pressure profile with a peak pressure drop of 50 MPa and a carrier frequency of 2.0 MHz in the focus of an ultrasound beam propagating in water. A 527-nm 10-ns laser pulse has been focused into the waist of the ultrasound beam at an angle of 90°. Backscattered photons have been recorded in a gated spectrum analyzer. It has been found that the Raman spectra at the times corresponding to the maximum and minimum acoustic pressures are significantly different. This feature has been used for point-to-point reconstruction of the acoustic pressure profile; for this purpose, the delay between the ultrasound and laser pulses is consequently increased with a step of 50 ns. It has been shown that, within the measurement error, the resulting changes in the position of the center of the stretching OH vibration band of water molecules in the Raman spectrum reproduce the acoustic pressure profile directly measured using a PVDF hydrophone at the laser sensing point. The results obtained can be used to develop a new method for remote diagnostics of the time profile of acoustic pressure and monitoring the local dynamic of the compression-tension processes in water up to critical pressures corresponding to the cavitation rupture, when the use of the hydrophone can lead to its damage.

中文翻译：

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拉曼光谱法诊断水中超声波束的局部时间

首次证明脉冲激光拉曼光谱可用于诊断局部声压分布，其峰值压降为50 MPa，载频为2.0 MHz，是在水中传播的超声波束的焦点。527 nm的10 ns激光脉冲已以90°的角度聚焦到超声束的腰部。反向散射光子已在门控频谱分析仪中记录。已经发现在对应于最大和最小声压的时间的拉曼光谱显着不同。此功能已用于声压曲线的点对点重建。为此，超声波和激光脉冲之间的延迟因此增加了50 ns。结果表明，在测量误差范围内，拉曼光谱中水分子拉伸OH振动带中心位置的最终变化再现了使用PVDF水听器在激光感测点直接测量的声压分布。当使用水听器时，获得的结果可用于开发一种新方法，用于对声压的时间曲线进行远程诊断，并监测水中的压力-拉伸过程的局部动态，直至达到与气蚀破裂相对应的临界压力。可能导致其损坏。