激光诱导等离子体对水OH伸缩振动受激拉曼散射的影响

Influence of laser-induced plasma on stimulated Raman scatting of OH stretching vibrational from water molecules

利用532 nm脉冲激光进行水的受激拉曼散射研究,通过改变激光焦点与水-空气界面的距离,获得截然不同的OH伸缩振动受激斯托克斯和反斯托克斯谱线.焦点距水-空气界面大于20 mm时,只存在±3400cm-1的斯托克斯和反斯托克斯谱线;焦点距离水-空气界面小于20 mm时,存在±3000和±3400cm-1的斯托克斯和反斯托克斯谱线;继续缩小焦点与水-空气界面的距离,3000 cm-1谱线被增强,而3400 cm-1谱线被削弱.研究结果表明,激光诱导水产生的等离子体增强了局部水分子的氢键,导致OH伸缩振动红移,同时过剩电子增强了水的OH伸缩振动受激拉曼散射.

532 nm pulse beam is used to induce the stimulated Raman scatting of water molecules. Different Stocks and anti- Stocks characteristic peaks of OH stretching vibrational from water molecules are obtained when the position of the focal spot is changed. The unique ~3400 cm-I Stokes characteristic peak with its anti-Stokes is present when the distance between focal spot and interface is fixed to be over 20 mm; both ~：3000 cm-I and ：1：3400 cm-1 with their anti-Stokes exist when the distance is reduced under 20 ram; both characteristic peaks are enhanced especially the 3000 cm-I peak whose change is more remarkable when the spot continues to move up. Experimental results indicate that laser-induced plasma generated from water molecules enhances the stimulated Raman scattering of OH stretching vibrational from water molecules by affecting hydrogen bonds between water molecules and OH from single water molecules.