微波驱动精细结构能级跃迁引起的电磁诱导负折射效应

本文通过建立Λ形四能级原子系统, 研究了微波驱动精细结构能级跃迁引起的电磁诱导负折射效应. 微波场作用于基态精细结构能级之间, 与不同精细结构能级之间的电偶极矩或磁偶极矩发生耦合, 使系统在某些频率处呈现负折射特性.同时, 两个耦合场各自激励一对基态和激发态之间的光学跃迁. 通过改变两个耦合场的频率失谐量控制负折射区域的频带宽度.结果表明, 耦合场失谐时出现负折射特性的频率范围比耦合场共振时迅速缩小, 而且耦合场负失谐和正失谐时的变化规律不同.     

大气压空气脉冲流光放电等离子体发射光谱分析

在大气压条件下采用尖-尖电极放电系统得到了稳定的放电等离子体, 并应用发射光谱方法对放电等离子体进行了实验研究。等离子体发射光谱呈现连续谱背景迭加分立谱的形式。连续谱背景来源于放电等离子体内轫致辐射和复合辐射过程; 分立谱归属为N2 C3∏u →B3∏g , N+, N, O的荧光辐射。N+荧光辐射对应的上能级电子组态为2s22p(2P0)3p和2s22p(2P0)3d, 能级高度介于20 eV和23.6 eV之间。实验还结合时间分辨光谱技术, 对放电等离子体中N2(336.8 nm)、N+(500.5 nm)、N+(399.7 nm)荧光信号进行时间分辨测量。结果表明, N2(336.8 nm)荧光首先出现, N+(500.5 nm、399.7 nm)荧光同时产生, 且滞后N2(336.8 nm)荧光约25 ns。根据时间分辨测量结果和相关参考文献, 文章对放电等离子体中N+的生成通道进行了分析。     

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.     

等离子体增强化学气相沉积氮化碳薄膜过程中的光学发射谱研究

利用光学发射谱技术对直流辉光放电等离子体增强的化学气相沉积氮化碳薄膜过程中的等离子体进行了原位诊断，结果表明主要的辐射有N2的第二正系跃迁、N2^ 的第一负系跃迁、CN和NH的紫外跃迁。研究了气源中氢气含量、放电电流及沉积气压的变化对N2（337.1nm)，N2^ (391.4nm)和CN(388.3nm)辐射强度的影响，并在此基础上探讨了这几种跃迁的激发机制，其结果为氮化碳合成中优化沉积参数、控制实验过程提供了依据。     

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.     

Photo-acoustic spectrum and detection of nitrogen dioxide

The photo-acoustic (PA) spectrum of nitrogen dioxide (NO2) in the range of 420 - 520 nm with a Nd:YAG pumped optical parametric generator and amplifier as radiation source is presented. The spectrum has a characteristic of banded structure superimposed on continuum. The banded structure of the spectrum can be assigned to NO2 B2B1 ←X2A1 transition. While the continual one comes from the chaos states of the first excited state A2B2 and the high vibration levels of the ground state X2A1. The relationship of PA signal with buffer gas pressure and NO2 concentration is measured. The PA signal intensity increases with buffer gas pressure and almost is invariable when the buffer gas pressure is more than 3.00×104 Pa. The PA signal intensity has linearity with NO2 concentration. The detection limit is about 2×10-5 on the basis of SNR = 1, however lower value of the detection limit can be expected by improving the apparatus properties.     

ANALYSIS OF F′0+u ION-PAIR STATE OF IODINE

The optical-optical double resonant multiphoton ionization (OODR-MPI) technique and the fluorescent excitation spectroscopy technique have been applied to the study of the F′0⁺_u ion-pair state of iodine. This paper presents OODR-MPI spectrum and fluorescent excitation spectrum of I₂ in the region of 54000-55300cm^-1 by the three-photon resonant, two-photon ionization (1+2+2) and (1+(1+1)+2) processes.     

NO分子A2∑态自发辐射寿命测量

利用激光光谱技术得到A2∑(v′=0,1)→X2Ⅱ(v"=0)跃迁在不同气压下的时间分辨谱,在此基础上得到A2∑(v′=0,1)两态的自发辐射寿命τ0分别为195.7 ns和180.1 ns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.     

辉光放电等离子体辅助XeCl准分子激光溅射沉积碳氮薄膜

利用直流辉光放电等离子体辅助的脉冲激光沉积技术在Si衬底上生长了碳氮薄膜.通过扫描电子显微镜、X射线衍射、X射线光电子能谱、俄歇电子能谱等多种手段,对薄膜的形貌、成分、晶体结构、价键状态等特性进行了分析和确定.结果表明,沉积薄膜为含有非晶SiN和晶态氮化碳颗粒结构,晶态成分呈多晶态,主要为α-C₃N₄相、β-C₃N₄相,晶粒大小为40—60nm.碳氮之间主要以C-N非极性共价键形式相结合. 关键词： 脉冲激光沉积 直流辉光放电 碳氮薄膜     

光浴对CH_3NH_3PbI_3薄膜光致发光量子效率的影响

研究了CH_3NH_3PbI_3薄膜在光浴条件下的光致发光量子效率演化行为。在光浴过程中,CH_3NH_3PbI_3薄膜的光致发光量子效率表现为先增大再减小的变化趋势。发光动力学测量实验表明,在光浴过程中,CH_3NH_3PbI_3薄膜的载流子复合寿命与光致发光量子效率具有相同的变化趋势,即先增大再减小。根据实验结果可以推断,光浴引发CH_3NH_3PbI_3薄膜发生两种物理过程,分别使其光致发光量子效率升高和降低。两种过程共同决定了CH_3NH_3PbI_3薄膜在光浴条件下的光致发光量子效率演化行为。