介质势垒放电(DBD)等离子体中NO荧光发射谱研究

利用介质阻挡放电 (DBD)等离子体技术对大气污染物NO分子进行了光谱研究 ,得到了低气压条件下放电等离子体在 2 1 0～ 2 80nm光谱范围内的荧光发射谱。该谱明显的表现为双峰结构 ,谱线均成对出现 ,强度分布符合Frank Condon原理 ,且最大峰值位置出现在 2 36nm处 ,将该组谱线归属为NO分子的A2 ΣA →X2 Π1 / 2 ,2 / 3 跃迁。荧光产生过程为 :基态NO分子与高能电子发生非弹性碰撞被激发至激发态A2 Σ 后自发跃迁回基态同时辐射出荧光。通过测量等离子体中NO分子和N2 分子 337nm谱线强度随时间的变化关系 ,初步证实了放电等离子体中存在的NO分子的分解机制为 :e NO→N O e,N NO→N2 O ,O NO→NO2 hν。     

NO分子A2Σ→X2Π双光子激光感生荧光光谱

以Nd∶YAG激光器抽运光学参变振荡器 /光学参变放大器做为激发源 ,得到了NO分子在 2 2 0～ 35 0nm波长范围内的双光子激光诱导荧光光谱 ,并将其归属于A2 Σ(ν′ =0 )→X2 Π(ν″ =1～ 8)跃迁 ,用最小二乘法拟合获得NO分子X2 Π态振动常量″ωe =(190 4 .7± 7.3)cm-1,″ωe ″xe =(14 .2± 1.2 )cm-1,″ωe″ye=- (0 .0 2 18± 0 .0 0 91)cm-1,及平衡位置的力常量k =(1.5 99± 0 .0 12 )× 10 3 N·m-1。计算了所得跃迁谱带的弗兰克康登因子及相对荧光强度 ,结果与实验观测值相符。这可为用激光诱导荧光光谱技术探测大气污染物NO分子提供理论及实验参考     

NO分子A2∑←X2Ⅱ跃迁的激光双光子荧光激发谱

以Nd:YAG脉冲激光器泵浦的光学参量发生器/放大器(OPG/OPA)作激发光源,获得了420～472nm波长范围内NO分子的双光子激光荧光激发谱,并利用此技术对NO分子的能级结构进行了实验研究,将所得谱线峰归属为NO(A2∑←X2Ⅱ)的跃迁,荧光强度随激光强度的二次方变化关系表明此过程是一双光子激发过程.利用实验所得峰值波长计算了NO(A2∑)态的基振动频率ωe和平衡位置的力常数k.通过对NO分子A2∑→X2Ⅱ跃迁的荧光时间分辨光谱进行实验研究,得到266 Pa气压下A2∑(v′=0)态的能级寿命τ=53.76ns.测量荧光寿命随气压的变化,利用曲线拟合得到NOA2∑(v′=0,1)两振动态的自发辐射寿命和无辐射跃迁驰豫速率常数.     

NO分子A~2Σ←X~2Π跃迁的激光双光子荧光激发谱

以Nd :YAG脉冲激光器泵浦的光学参量发生器 放大器 (OPG OPA)作激发光源 ,获得了 4 2 0～ 4 72nm波长范围内NO分子的双光子激光荧光激发谱 ,并利用此技术对NO分子的能级结构进行了实验研究 ,将所得谱线峰归属为NO(A2 Σ←X2 Π)的跃迁 ,荧光强度随激光强度的二次方变化关系表明此过程是一双光子激发过程。利用实验所得峰值波长计算了NO(A2 Σ)态的基振动频率ωe 和平衡位置的力常数k。通过对NO分子A2 Σ→X2 Π跃迁的荧光时间分辨光谱进行实验研究 ,得到 2 6 6Pa气压下A2 Σ(v′ =0 )态的能级寿命τ=5 3 76ns。测量荧光寿命随气压的变化 ,利用曲线拟合得到NOA2 Σ(v′=0 ,1) 两振动态的自发辐射寿命和无辐射跃迁驰豫速率常数     

Variation of electronic transition moment versus internuclear distance for NO (A2∑→ X2∏) transition

Two-photon laser-induced fluorescence spectrum (TP-LIF) of NO is obtained with a Nd:YAG pumpedoptical parametric generator and amplifier as radiation source. Spectral intensity distribution shows thatthe electronic transition moment for NO (A2∑→ X2∏) transition varies significantly with inter-nucleardistance. The variation relationship of the electronic transition moment versus inter-nuclear distance isdeduced with polyminal fit procedure. The spontaneous radiative coefficients for NO (A2∑→ X2∏)transition from v′ = 0, 1 are obtained by combing this transition moment variation with the measurementsof spontaneous radiative lifetime.     

Variation of electronic transition moment versus internuclear distance for NO (A~2∑→X~2Ⅱ) transition

Two-photon laser-induced fluorescence spectrum (TP-LIF) of NO is obtained with a Nd:YAG pumped optical parametric generator and amplifier as radiation source. Spectral intensity distribution shows that the electronic transition moment for NO (A2∑→ X2Ⅱ) transition varies significantly with inter-nuclear distance. The variation relationship of the electronic transition moment versus inter-nuclear distance is deduced with polyminal fit procedure. The spontaneous radiative coefficients for NO(A2∑→ X2Ⅱ) transition from v'= 0,1 are obtained by combing this transition moment variation with the measurements of spontaneous radiative lifetime.     

Resonance-enhanced multiphoton ionization of NO via X2П→A2∑ transition

The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420-480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral linescan be attributed to NO X2П(v" = 0, 1) → A2∑(v' = 0, 1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A2∑+ and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.     

基于扫描激光器的边孔光纤光栅温度压力传感系统

研究了一种基于波长扫描激光器的光纤温度压力测量系统.光纤传感头为边孔光纤光栅,利用其特有的双折射特性产生双反射峰,以实现对温度和压力的同时测量.系统采用嵌入式开发技术,将激光波长扫描、光谱数据采集和以牛顿最小二乘法为核心的光栅解调算法高度整合于一体,极大降低了光纤传感系统的体积与成本.实验结果表明,在温度10~50℃、压力0~1.2 MPa时,双反射峰对应温度与压力的变化均呈现良好的线性响应特性;系统的波长解调准确度可达1pm,温度及压力的分辨率分别达到0.1℃和0.1 MPa.该系统可为温度、压力的参量测量提供低成本、小型化、性能可靠的解决方案.     

Resonance-enhanced multiphoton ionization of NO via X~2II-A~2Σ transition

The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X2II(v=0,1)-A2(v' = 0,1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A2E+ and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.     

NO分子A~2Σ态自发辐射寿命测量

利用激光光谱技术得到A2Σ(v′=0,1)→X2Π(v″=0)跃迁在不同气压下的时间分辨谱,在此基础上得到A2Σ(v′=0,1)两态的自发辐射寿命τ0分别为195.7ns和180.1ns及无辐射驰豫速率kq分别为4.73×104kg-1ms和3.91×104kg-1ms.同时将时间分辩谱上产生较大波动原因初步归结为较宽的激光脉宽所引起的量子拍频现象.