共查询到17条相似文献,搜索用时 46 毫秒
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汽车排放的主要污染物为CO,HC,NOx(x=1,2),SO2,Pb,苯丙芘,固体颗粒等[1],其尾气的检测对维护人类自身健康具有十分重要的意义.共振增强多光子电离光谱(Resonant Enhanced Multi-Photonionization,REMPI)是一种超灵敏光谱检测技术,它的灵敏度比LIF(Laser InducedFluorescence)还要高.1979年,Brophy和Rentttner[2]提出了REMPI可以作为检测大气污染的方法.后来,不同的研究小组采用了不同的REMPI方案对大气污染类分子进行了测量研究[3-6].由于采用可调谐染料激光器为光源,可以使用同一种染料对几种具有相近特征波长的分子进行同时测定.本文报 相似文献
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利用Ar/CF4、Ar/CF2Cl2或Ar/CF3COOH混合气体的直流脉冲放电产生CF自由基,观测了260~360nm范围内转动分辨的CF自由基双光子共振增强多光子电离谱。分析表明,该段光 谱对应于CF自由基3pπD2Πr(ν'=2~6,r=3/2,1/2)←←X2Πr(ν"=0,r=3/2,1/2)的共振激发。对观测的振动带进行了转动分析,并获得了3p里德堡态的转动常数和自旋-轨道分裂值。 相似文献
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正-溴代烷烃的紫外光解动力学研究 总被引:1,自引:0,他引:1
利用共振增强多光子电离飞行时间质谱(REMPI-TOFMS),研究了长链正-溴代烷烃R-Br(R为正烷烃基)(C2H5Br,n-C3H7Br,n-C4H9Br)在234及267nm附近的光解动力学.溴碎片来源于R-Br的直接解离:R-Br→R Br(^2P3/2)/Br(^2P1/2),根据测定的离子信号强度,得到了Br^n与Br的分支比N(Br^*)/N(Br)及相应的相对量子产额φ(Br^*)和φ(Br).φ(Br^*)与激光波长及分子结构显示了一定的依赖关系,将实验结果用CH3Br的解离模型进行拟合,得到了长链R-Br的光解动力学行为的定性解释。 相似文献
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在分子束中用高温热解3-碘代丙烯的方法产生烯丙基,并结合飞行时间质谱和2+1共振增强多光子电离技术,从实验上观测到了烯丙基从基态到6~8eV之间的6个电子态3dxz, 3dxy,ns(n=4,6,7,8)的电子振动光谱.在ns的Rydberg态电子振动光谱中可以观测到v7(∠CCC弯曲振动)约为430cm-1的振动级数.由Rydberg公式拟合得到烯丙基的绝热电离能为(65641±20)cm-1((8.138±0.002)eV). 相似文献
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测定了卤化氢(HCl, HBr 和HI) (2+1)共振增强多光子电离(REMPI)光谱, 采用模拟计算法分析推导出转动常数、谱带源以及Ω态振动谱带的同位素位移值. 得到的HCl数据同Green等人用常规分析法所推导的结果极为吻合. 得出8条振动谱带,其中包括V(1∑+)态, E(1∑+)的v'=4态以及HBr的5个新谱带, 此外还推导出HI的E态v'=1的4个振动谱带光谱参数. 观测了V和E态之间因同类相互作用而产生的不规则能级间距、转动参数和同位素位移. 讨论了HCl和HBr的E态和V态振动谱带中的转动谱线序列O和S对Q的强度比变化,提出了双光子激发机理. 相似文献
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溴代烷烃在紫外波段的光解离过程 总被引:1,自引:3,他引:1
在飞行时间质谱仪中,采用波长为234 nm和267 nm的激光,研究溴代烷烃CHBr3、CH2Br2、C2H5Br及C2H4Br2的光离解过程.在UV激光的作用下,溴代烷烃分子主要发生的是吸收1个光子解离出Br原子,然后继续吸收光子发生Br原子的(2+1)共振增强多光子电离的过程.其中由溴代烷烃分子解离得到的Br原子可能存在着两种布居:基态Br(2P03/2)及激发态Br*(2P01/2).研究解离得到的Br原子的分支比 N(Br*)/N(Br),并给出测量结果:溴代烷烃分子解离得到的Br原子在267 nm激光作用下的分支比明显大于在234 nm激光作用下的结果.对此多光子过程的机理,也进行了分析讨论. 相似文献
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碘代烷烃在532 nm激光作用下多光子电离解离机理 总被引:3,自引:0,他引:3
利用532nm的激光对碘代烷烃(碘甲烷、碘乙烷、碘代正丙异丙烷)分子作了多光了电离解离(MPID)质谱(MS)研究,在532nm激光作用下,CH3I分子吸收532nm激光双光子的能量,进入A带的IA2态,继续吸收光子上泵浦至电离态形成母体离子CH3I,然后再形成碎片离子;而其它几个碘代烷烃吸收双光子的能量进入A带后均形成中性碎片,中性碎片再吸收光子经一系列电离解离形成碎片离子,此外,本文还通过对同 相似文献
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The (3 + 1) photon ionization spectra of SiH_4 have been measured. A basically continuous spectrum was recorded in laser wavelengths from 428 to 458 nm.Two vibrational progressions were found in the UV laser region of 347-392 nm, anda fine structure of the band at 363.5 nm was assigned.The fragment ions were detected by a time-offlight mass spectrometer. No parent ion SiH_4~+ was observed whereas SiH_2~+ and SiH_3~+ were the major products. The ratio of SiH_2~+/SiH_3~+ was approximately equal to that of single photon ionization at the same energy, but the fraction of Si~+ was increased. Some additional bands appeared in Si~+ spectrum in the range of 384-390 nm implicating that the increased Si~+ might be generated from SiH_2~+ and SiH~+ ions. 相似文献
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(1+1) Resonance‐Enhanced Multiphoton Ionization and Photodissociation Study of CS2 via the 1B2 State
Zhengfa Hu Dr. Wei‐Bin Lee Xiao‐Peng Zhang Dr. Pei‐Ying Wei King‐Chuen Lin Prof. 《Chemphyschem》2008,9(3):422-430
(1+1) resonance‐enhanced multiphoton ionization (REMPI) spectra of CS2 and molecular dissociation dynamics are investigated using a time‐of‐flight mass spectrometer equipped with velocity imaging detection. The REMPI spectra via a linear‐bent →1B2( ) transition are acquired in the wavelength range of 208–217 nm. Each ro‐vibrational band profile of the 1B2( ) state is deconvoluted to yield the corresponding predissociative lifetime from 0.3 to 3 ps. Upon excitation at 210.25 and 212.54 nm, the resulting images of S+ and CS+ fragments are analyzed to give individual translational energy distributions, which are resolved into two components corresponding to the CS+S(3P) and CS+S(1D) channels. The product branching ratios of S(3P)/S(1D) are evaluated to be 5.7±1.0 and 9.6±2.5 at 210.25 and 212.54 nm, respectively. Despite the difficulty avoiding the effect of multiphoton absorption, the molecular dissociation channel is verified to prevail over the dissociative ionization channel of CS2. The anisotropy parameters for the triplet and singlet channels are determined to be ~0.8 and 1.1–1.3, respectively, suggesting that the predissociative state should have a bent configuration with a short lifetime. 相似文献
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Photoelectron Circular Dichroism of Bicyclic Ketones from Multiphoton Ionization with Femtosecond Laser Pulses 下载免费PDF全文
Christian Lux Prof. Dr. Matthias Wollenhaupt Cristian Sarpe Prof. Dr. Thomas Baumert 《Chemphyschem》2015,16(1):115-137
Photoelectron circular dichroism (PECD) is a CD effect up to the ten‐percent regime and shows contributions from higher‐order Legendre polynomials when multiphoton ionization is compared to single‐photon ionization. We give a full account of our experimental methodology for measuring the multiphoton PECD and derive quantitative measures that we apply on camphor, fenchone and norcamphor. Different modulations and amplitudes of the contributing Legendre polynomials are observed despite the similarity in chemical structure. In addition, we study PECD for elliptically polarized light employing tomographic reconstruction methods. Intensity studies reveal dissociative ionization as the origin of the observed PECD effect, whereas ionization of the intermediate resonance is dominating the signal. As a perspective, we suggest to make use of our tomographic data as an experimental basis for a complete photoionization experiment and give a prospect of PECD as an analytic tool. 相似文献
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CH自由基在燃烧化学、星际化学、化学发光和化学激光研究中占有重要的地位,并且作为最简单的碳氢化合物,CH自由基是理想的理论计算模型分子,在理论研究领域中也有着重要的地位.因此 ,多年来人们对CH自由基进行了大量的研究[1 -9],但是对于CH自由基,到目前为止大部分局限于低激发态的研究,对于较高激发态的研究报导则很少见.Chupka等[2 -6]用(2 1)REMPI方法获得了CHD态的v=2振动能级光谱.然而后来Tjossem和Smyth[7]测量了同波段的REMPI光谱,发现他们测得的光谱谱峰强度与… 相似文献
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S. Yu. Ketkov H. L. Selzle E. W. Schlag S. N. Titova L. V. Kalakutskaya 《Russian Chemical Bulletin》2004,53(8):1667-1669
Two-photon ionization of the nickelocene molecules cooled in a supersonic jet was performed for the first time by simultaneous excitation of (5–C5H5)2Ni with two tunable nano- second dye lasers. The one-photon transition from the HOMO to the Rydberg R4p level was used as the initial step of the multiphoton excitation. In a one-color experiment, the conditions were found for generation of the intact molecular ion, (5–C5H5)2Ni+, as the only ionic product of the multiphoton ionization. The use of an intense pulse of the second dye laser lead to an increase in the yield of the molecular ion.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1604–1606, August, 2004. 相似文献