共振增强水分子O-H伸缩振动受激拉曼散射

Resonance enhanced stimulated Raman scattering of O-H stretching vibration in water molecule

受激拉曼散射(SRS)技术是获得相干辐射、探索分子结构的有力手段。利用Nd:YAG 532 nm激光作用于水分子,并与650 nm连续(CW)激光联用,极大增强了水分子的O-H伸缩振动受激拉曼散射。当有1 mW CW激光引入时,在3392 cm^(-1)处的O-H伸缩振动SRS峰的强度增加了一个数量级。同时,获得了两个新的低频肩峰(3356 cm^(-1)和3288 cm^(-1))。CW激光不仅降低了SRS阈值,而且提高了SRS强度。导致此现象的物理机制是由于532 nm泵浦激光和650 nm CW激光之间的频率差与水分子O-H伸缩振动频率相匹配,分子振动与两束激光差频形成共振。此研究为共振增强其他弱拉曼模式提供了参考。

Stimulated Raman scattering(SRS)technology is a powerful method to obtain coherent radiation and explore molecular structure.SRS of O-H stretcing vibration in water molecules is studied,and it is found that SRS of water molecules excited by 532 nm laser is greatly enhanced by the application of CW(continuous-wave)seeding laser with 650 nm.When 1 mW CW laser power is introduced,the normalized SRS intensity of O-H stretching vibration at 3392 cm^(-1) is increased by an order of magnitude,and at the same time,two new lower frequency shoulder peaks(3356 cm^(-1) and 3288 cm^(-1))are also observed.The introduction of CW seeding laser not only lowers the threshold of SRS,but also increases the intensity of SRS.The mechanism of the enhancement of SRS intensity is attributed to that the frequency difference between pump laser(532 nm)and CW seeding laser(650 nm)matches the O-H stretching vibrational frequency of water molecule,resulting in the resonance between molecular vibration frequency and the difference frequency of the two lasers.This work shows the possibility of using resonance methods to enhance weak Raman vibration modes.