N2O分子C1Π态的吸收光谱及解离动力学.pdf

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1、物理化学学报(WuliHuaxueXuebao)Acta尸hys．一Chim．Sin．，2010，26(1)：94—98January[Article】WWW．whxb．pku．edu．cnN20分子CⅡ态的吸收光谱及解离动力学甄承胡亚华刘世林周晓国(合肥微尺度物质科学国家实验室(筹)，中国科学技术大学化学物理系，合肥230026)摘要：通过四波混频差频的方法产生高分辨的真空紫外激光，用以测量143．6至146．9am范围内的射流冷却N20分子吸收光谱，对应于c，x的吸收跃迁．谱图显示出三个分立的振动谱峰叠加在宽吸收背景上，谱峰间隔分别是521

2、和482cm～．前人的高精度量子化学计算表明C1H态在N—0键长方向表现为无势垒的排斥态，而在N～N键伸缩及NO弯曲振动方向则表现为束缚态，因此观测到的振动谱峰被归属为激发态的Feshbach共振．通过反Fourier变换可以得到Feshbach共振对应的非稳定周期轨道的特征周期为61fs，相应的振动频率为546cm～．鉴于这一频率与弯曲振动频率非常接近，非稳定周期轨道被认为是由CH态的弯曲振动与解离运动相互作用而形成的，N—_N伸缩振动没有参与形成非稳定周期轨道．由此，N20分子CH态光激发一解离过程得以清晰地阐述．关键词：吸收光谱；一氧化二

3、氮；真空紫外光；解离中图分类号：0644；0643AbsorptionSpectrumandDissociationDynamicsoftheCI1StateofNz0ZHENChengHUYa—HuaLIUShi—LinZHOUXiao—GuotHefeiNationalLaboratoryforPsicalSciencesattheMicroscaleDepartmentofChemicalPhysics,UniversityofScienceandTechnologyofChina，Hefei230026，PR．China)Abstrac

4、t：TheabsorptionspectrumoftheN2Omoleculeinthewavelengthrangeof143．6-146．9amwasmeasuredunderthejet-cooledconditionbyusingthehighresolutionvacuumultravioletradiation，whichwasgeneratedbyresonance—enhanceddifference—frequencymixing．correspondingtOtheCntransition．Threevibrationalb

5、andswereobservedwithfrequencyintervalsof521and482cm-1，andtheyweresuperimposedonawideabsorptionbackground．Previoushigh—levelquantumchemicalcalculationsindicatethattheC，7stateofN20isdissociativealongtheN—_oelongation．whileitisboundalongtheN—NbondstretchingorN2Obending．Therefor

6、e．theobservedvibrationalprogressionisaFeshbachresonanceofthedissociativetransitionstate．Fromananti—Fouriertransformationanalysis，therecurrenceperiodoftheunstableperiodicorbitoftheFeshbachresonancewasfoundtobe61fsandthecorrespondingvibrationalfrequencywas546cm．Sincethisvibrat

7、ionalfrequencyisclosetothe~equencyofthebendingmotion．theunstableperiodicorbitismostlycomposedofthebendingmotionoftheC，7statecoupledwithdissociation．TheN—Nstretchingvibrationdoesnotparticipateinitsformation．Therefore．wedescribetheexcitation—dissociationdynamicsoftheCⅡstateofN

8、20clearly．KeyWords：Absorptionspectrum；N20；Vacuumultraviolet；Dissociation作为一