飞秒光学外差光学克尔效应和低频拉曼光谱技术研究离子液体[bmim][pf_6]的低频光谱

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1、物理化学学报(WuliHuaxueXuebao)964ActaPhys.鄄Chim.Sin.,2010,26(4)：964-970April[Article]www.whxb.pku.edu.cn飞秒光学外差光学克尔效应和低频拉曼光谱技术研究离子液体[bmim][PF6]的低频光谱*王维吕荣于安池(中国人民大学化学系,北京100872)摘要：利用飞秒光学外差光学克尔效应技术获得了咪唑类离子液体1鄄丁基鄄3鄄甲基咪唑六氟磷酸盐([bmim][PF6])体系中反映分子间相互作用的低频光谱.结果分析中,

2、利用Brownian振子时间相关函数的精确表达式对光学克尔效应动力学数据中的核振动部分进行模拟,在时域上获得各个振动组分的时间演化行为,并进而通过快速Fourier变换获得各个振动组分的频域光谱和总加和光谱.此外还利用低频拉曼光谱技术测量了离子液体[bmim][PF6]的低频光谱,并和飞秒光学外差光学克尔效应实验的结果进行对比,发现两种方法获得的低频光谱相近.实验结果表明Brownian振子时间相关函数的精确表达式可用来解析离子液体体系中低频振动的时间演化行为.关键词：低频拉曼光谱;飞秒光学外差光

3、学克尔效应;离子液体;[bmim][PF6];低频振动;Brownian振子中图分类号：O643LowFrequencySpectrumofIonicLiquid[bmim][PF6]StudiedbyFemtosecondOpticallyHeterodyne鄄DetectedOpticalKerrEffectSpectroscopyandLowFrequencyRamanSpectroscopy*WANGWeiL譈RongYUAn鄄Chi(DepartmentofChemistry,Renmi

4、nUniversityofChina,Beijing100872,P.R.China)Abstract：Thelowfrequencyvibrationalspectrumthatreflectstheintermolecularinteractionofanimidazoliumcationionicliquid1鄄butyl鄄3鄄methylimidazoliumhexafluorophosphate([bmim][PF6])wasstudiedbyfemtosecondopticallyhe

5、terodyne鄄detectedopticalKerreffect(OHD鄄OKE)spectroscopy.SeveralexplicittimecorrelationfunctionsoftheBrownianoscillatorwereusedtosimulatethekineticnuclearcontributionofthefemtosecondOHD鄄OKEdata.Thetimeevolutionbehaviorofeachindividualoscillatorinthetim

6、edomainwasobtained.WeobtainedthefrequencyspectrumforeachoscillatorinthefrequencydomainbythefastFouriertransformtheorem.Inaddition,wealsomeasuredthelowfrequencyvibrationalspectrumof[bmim][PF6]bylowfrequencyRamanspectroscopy.Theselowfrequencyspectraobta

7、inedbylowfrequencyRamanspectroscopyandbyfemtosecondOHD鄄OKEspectroscopyshowverysimilarcharacteristics.TheseresultsdemonstratethattheexplicittimecorrelationfunctionoftheBrownianoscillatorcanbeusedtoresolvethetimeevolutionbehaviorofthelowfrequencyvibrati

8、onmodeinionicliquids.KeyWords：LowfrequencyRamanspectroscopy;Femtosecondopticallyheterodyne鄄detectedopticalKerreffect;Ionicliquid;[bmim][PF6];Lowfrequencyvibration;BrownianoscillatorReceived:December29,2009;Revised:January21,2010;PublishedonWeb