OCS的多光子电离高分辨光电子能谱

硫氧化碳OCS是线性三原子分子，这类小分子的激发态、离子态能级结构、能级之间的相互作用及电离过程，是研究中所关心的问题．Tanaka等[1]和Kopp[2]测量了OCS的VUV吸收光谱，Frey和Schlag等[3]以同步辐射光源，用光电离共振（PIR）谱方法、Kovac[4]和Wang，Shirley等[5]以Hel为电离光源，分别采用传统的光电子能谱和高分辨光电子能谱技术研究了CO2、CS2和OCS分子从电子振动基态吸收单个光子而电离的过程．Yang和Anderson等问为了作选态的离子一分子反应利用可调谐激光rt光子吸收将OCS选择激发到某一中间态，OCS再吸收光子后…     

通过中间解离态的共振增强多光子电离光电子能谱研究解离动力学

通过与NH3 的第一快速预解离激发态 A1A″2 共振的 ( 1 1)多光子电离光电子能谱 ,得到了与共振Raman光谱等价的N—H伸张振动带系 ,提出了一种新的基于bound free bound跃迁的多光子电离光电子能谱研究解离动力学的方法     

飞秒脉冲作用下氯丙烯的多光子解离和电离动力学

The dissociation and photoionization dynamics of C₃H₅Cl were studied at 200, 400, and 800 nm with femtosecond laser pulses. The time-of-flight mass spectra, laser power index and photoelectron images were recorded. At short wavelength (200 nm), ionization of the parent molecule was found to be the dominant channel, while other ions were generated by the dissociation of C₃H₅Cl⁺. With the shift to long wavelength (e.g., 800 nm), fragment ions became dominant, and were generated through the multiphoton ionization of neutral fragments after the photodissociation of C₃H₅Cl. These results imply that photodissociation plays a significant role at long wavelength, because neutral fragments are supposed to be generated from the intermediate states reached by 800 nm photons. At 400 nm, the dissociation on the intermediate states is also critical, but is not as high as that at 800 nm. Taken together, our results demonstrate that the dissociation/ionization behaviors of allyl chloride are wavelength-dependent, and reveal the complex dynamics of allyl chloride at 200, 400 and 800 nm.     

OCS分子的共振多光子电离光谱

OCS分子的真空紫外吸收光谱早有研究,但有关OCS分子的多光子电离光谱尚未见报导。我们利用可调脉冲激光器,研究了OCS分子的共振多光子电离光谱。首次观察到OCS分子在277—285nm波长范围内的多光子电离光谱。OCS由硫氰酸铵和硫酸反应制取,经多次低温蒸馏纯化。产物通过FT-IR红外光谱和     

新型单光子电离和光电子电离复合电离源的研究及应用

复合电离源在单光子电离模式下可以产生分子离子信号,易于确定分子量;在光电子电离模式下,70 eV电子能量可以产生含有物质结构信息的碎片峰,实现物质的结构鉴定.两种电离模式可以实现毫秒级迅速切换.本研究通过提高光程降低了单光子电离模式下的检出限.在单光子电离模式下,对苯的检出限为50 μg/m3(累加时间为4s);光电子...     

370-410nm波段CS2的共振多光子电离研究

对CS。人们曾做过广泛的研究，其中光谱研究以吸收谱最多，CSZ的解离动力学的研究也比较多．Butler等［‘］用193urn激光单光子激发CSZ获得CS碎片，研究了CSZ的解离．Seaver等［’1分别用266DD和193。激光多光子电离CSZ．但他们都是在固定激发波长下研究CSZ的解离．在370－405u     

丙酮团簇的多光子电离解离与结构计算

用355nm激光多光子电离解离飞行时间质谱观测到在超声分子束中形成的最多为12个分子的团簇离子及其碎片.用密度泛函方法对n=2～5的丙酮团簇结构进行计算,给出了优化构型及其基态能量.结果表明,两个丙酮分子组成团簇时稳定结构为近似垂直构型.3～5个丙酮分子组成团簇时以环状结构最稳定.     

甲硅烷的多光子电离

本文测量了SiH_4的(3+1)电离光谱。在激光波长428—458nm基本上是一个连续谱,在激光紫外区347—392nm,得到两个振动前进带组,并标识了一个位于363.5nm的谱带精细结构。用飞行时间质谱仪检测了碎片离子,没有观察到母体离子SiH_4~+,主要的产物离子是SiH_2~+和SiH_3~+,SiH_2~+和SiH_3~+离子产率的比值近似等于相同能量下的单光子电离结果,但Si~+的产率明显增加。在384—390nm范围的Si~+离子的光谱中比其它离子的光谱多出一些谱带,其增加的Si~+可能来自SiH_2~+和SiH~+离子的离解过程。     

卤化氢共振增强多光子电离光谱

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.     

乙胺和二甲胺分子(n_N,3s)里德堡态共振的多光子电离

MPI质谱研究作为化学分析和研究光物理过程的工具受到广泛的重视[1－4]．REMPI的特征过程是，首先分子吸收。个光子共振激发到中间态，然后处于中间激发态的分子再吸收n个光子激发到电离连续区[5]．REMPI的谱特征可以给出中间态分布的详细信息[6]，利用REMPI过程可研究单光子跃     

Velocity Mapping Studies of Vibrational Energy Disposal Following Methyl Iodide Photodissociation

In this paper previous results are compared for two different types of velocity mapping studies which probe vibrational energy disposal following the A-band photodissociation of methyl iodide, CH₃I + hv → CH₃ (v) + 1(²P_3/2), 1*(²P_1/2). Full three-dimensional state-specific speed and angular distributions of the nascent fragments have been recorded for the photoelectrons, iodine atoms, and methyl radicals, using state- and mass-selective (2+1) resonance-enhanced multi-photon ionization (REMPI)/time-of-flight spectrometry. Two sources of information on the vibrational energy disposal are available from velocity mapping: (a) the photoelectron images, which give information on the initial stages of vibrational excitation in electronically excited CH₃I, and (b) methyl radical images, which indicate the final energy disposal channels. Even though the two signals are believed to probe very different time-scales of the dissociation process, good agreement between the two is found for the vibrational energy disposal trends. Several trends found in the data for methyl iodide photodissociation indicate that readjustment of the ab initio multi-dimensional potential energy surfaces calculated for this molecule appears to be needed.     

光电子成像方法研究Xe时间分辨多光子电离过程

利用自行研制的离子成像检测器研究了Xe的飞秒时间分辨双色多光子电离过程.Xe的408nm多光子电离对比实验结果表明,该离子成像检测器与相应的进口产品具有相近的光电子能量分辨率.在272nm飞秒激光作用下,3光子电离产生能量为1.57和0.26eV的光电子,分别对应于Xe+的两个自旋态;在408nm飞秒激光作用下,还观察到第一级阈上电离产生的光电子.在双色飞秒时间分辨实验中,随着两束光相对时间的改变,光电子能谱出现了一系列的变化;随着两束光时间重合程度的增加,由双色多光子电离(3+1'或4'+1)产生的光电子信号逐渐加强;在第二束光的作用下,由第一束单色光产生的光电子出现能量红移,第二束光同时也导致中间态布居数减少.这种光电子能谱的红移现象反映了原子体系中激光场诱导有质动力势的时间分辨动态调制过程.     

Predissociation Dynamics of B State of Methyl Iodide with Femtosecond Pump-probe Technique

The predissociation dynamics of B Rydberg state of methyl iodide is studied with femtosecond two-color pump-probe time-of-°ight spectra at pump pulse of 400 nm and probe pulse of 800 nm. The dominant product channels are the CH3I+ and CH3+ formation. The time-dependent signals for CH3I+ and CH3+ ions are obtained. Both of the signal curves can be ˉtted by biexponential decays with time constants of ?1 and ?2, ?1 is assigned to the lifetimes of high Rydberg states, which can be accessed by absorbing three 400 nm pump pulses and ?2 re°ects the dynamics of B Rydberg state, which is accessed with two pump pulses. The lifetime of B Rydberg state is determined to be about 1.57 ps, which is incredibly consistent with the previous studies. The results were interpreted as a multiphoton dissociative ionization processes.     

呋喃分子多光子电离解离过程的反应通道

The multiphoton ionization and fragmentation pathway of furan at 450nm is analyzed on the basis of statistical theory and Ladder-Switching model. Our calculation indicates that fragmentation takes plase after furan molecules absorb six photons of 450nm, C+ begins to appear after absorption of nine photons, production of C2+ ions needs absorption of at least 15 photons. Our interesting result is that C+ ions is produced by dissociation of C3H+, CH2+ and C3+ ions, not of C2+ ions. Theoretically computed relative abundance of C+/C2+ after absorption 15photons agrees well with our experimental results.     

甲胺分子多光子电离质谱研究

胜多光子电离飞行时间质谱法，利用可调谐脉冲激光器，测得了甲胺分子在不同激光波长和激光功率下的多光子电离和解离产物。母体离子ＣＨ３ＮＨ＾＋２的离解速常数随激光发波长的增大而减小。     

à 3E态CH3N自由基的稳定性

观察到了CH_3N自由基Ã ~3E←X~3A_2体系317-272 nm的荧光激发谱, 特别讨论了振动激发的Ã 态的稳定性. 报导了v_3~′=6态的色散荧光和荧光时间谱, 该态在240 Pa下的寿命大约是80 ns. 实验表明Ã ~3E 态CH_3N自由基是稳定的, 势能面至少距振动基态4800 cm~(-1)内是束缚的, 异构化或预离解作用并不重要.     

Ab initio Study on Ionization Energies of 1-Methyl-hypoxanthine

Six low-lying tautomers of 1-methyl-hypoxanthine have been studied at the B3LYP/aug-cc-pVDZ level. Two tautomers N7H and N9H with the comparable energies are far more stable than the others. The vertical ionization energies of the tautomers calculated with ab initio electron propagator theory in the P3/aug-cc-pVDZ approximation are in agreement with the experimental data from photoelectron spectroscopy. According to the calculated relative energies and the comparison between the simulated and the experimental photoelectron spectra, it demonstrates that there are at least two tautomers of 1-methyl-hypoxanthine in the gas-phase experiments.     

Multiphoton ionization of metal cluster complexes Os3(CO)12 and Ir4(CO)12: Determination of the ionization energy and coordination energy of the complex ions

Multiphoton ionization and the subsequent dissociation process of metal cluster complexes Os₃(CO)₁₂ and Ir₄(CO)₁₂, prepared in a supersonic jet, were studied by means of multiphoton ionization with time-of-flight (TOF) mass detection. The ionization energies of Os₃(CO)₁₂ and Ir₄(CO)₁₂ were determined to be 7.95 and 8.3 eV, respectively, from the laser wavelength at the ionization threshold. The coordination energies of Os₃(CO)₁₂⁺ and Ir₄(CO)₁₂⁺ ions were also determined to be 1.6 and 1.2 eV, respectively, from the excitation energy needed to cause the appearance of fragment ions. The observed values agreed reasonably well with the ones calculated by using the density functional theory method.