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间甲基苯甲醚分子有顺式和反式两个转动异构体. 利用单光共振双光子电离技术和质量分辨阈值电离技术,研究了间甲基苯甲醚分子顺反异构体的基态到第一电子激发态(S1←S0)的跃迁和阈值电离. 得到顺式、反式间甲基苯甲醚分子S1态的激发能(E1)分别为(36049±2)和(36117±2)cm-1,绝热电离能(Ip)分别为(64859±5)和(65110±5)cm-1. 结合从头算法和密度泛函理论的量子化学计算,解释了顺式、反式间甲基苯甲醚分子E1和Ip存在差异的原因,并且对S1态和离子基态D0态出现的谱峰进行了标识. 间甲基苯甲醚分子顺反异构体在S1态和D0态的活性振动主要是甲基转动、面内环的运动和与取代基相关的弯曲振动. 间甲基苯甲醚分子的S1态振动光谱、D0态离子光谱以及理论计算均表明这两个转动异构体在D0态的几何构型与S1态的中性几何构型相比有较大改变,取代基与取代基、取代基与苯环间的相互作用强度高低次序为:S0<S1<D0. 相似文献
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间甲基苯甲醚分子有顺式和反式两个转动异构体.利用单光共振双光子电离技术和质量分辨阈值电离技术,研究了间甲基苯甲醚分子顺反异构体的基态到第一电子激发态(S1←S0)的跃迁和阈值电离.得到顺式、反式间甲基苯甲醚分子S1态的激发能(E1)分别为(36049±2)和(36117±2)cm-1,绝热电离能(Ip)分别为(64859±5)和(65110±5)cm-1.结合从头算法和密度泛函理论的量子化学计算,解释了顺式、反式间甲基苯甲醚分子E1和Ip存在差异的原因,并且对S1态和离子基态D0态出现的谱峰进行了标识.间甲基苯甲醚分子顺反异构体在S1态和D0态的活性振动主要是甲基转动、面内环的运动和与取代基相关的弯曲振动.间甲基苯甲醚分子的S1态振动光谱、D0态离子光谱以及理论计算均表明这两个转动异构体在D0态的几何构型与S1态的中性几何构型相比有较大改变,取代基与取代基、取代基与苯环间的相互作用强度高低次序为:S0S1D0. 相似文献
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利用共振双光子电离(R2PI)技术和质量分辨阈值电离(MATI)技术来研究2, 5-二氟苯酚分子。实验所测得的顺式、反式2, 5-二氟苯酚分子电子激发能E1分别为36448和36743 cm-1,绝热电离能分别为71164和71476 cm-1。这两个顺反转动同素异构分子在电子激发S1态与离子D0态活性振动主要是由于面内环变形和与取代基相关的弯曲振动。分析2, 5-二氟苯酚分子的振动光谱、D0态离子光谱以及理论计算均表明这两个转动异构体在D0态的几何构型与S1态的中性几何构型相当相似。 相似文献
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A method is devised better to resolve the subbands of the ground vibronic band in the mass‐analyzed threshold ionization (MATI) spectrum of CD3I. By selective photodissociation of CD3I+ in these subbands, high‐resolution spectra for the à 2A1← 2E3/2 transition are recorded. Spectral analysis confirms our previous suggestion that these subbands are due to cations in different rotational K states; this demonstrates the capability of MATI to generate rovibronically selected ion beams. By using the rotational constants of CH3I+ and CD3I+ obtained by spectral analysis, the zero‐point‐level geometries of the cations in the 2E3/2 and à 2A1 states are determined. To the best of our knowledge, this is the first time that the capability of MATI–PD to determine the geometry of a gas‐phase polyatomic cation in an excited electronic state is demonstrated. 相似文献
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Kaja Schubert Dr. Lucas Schwob Simon Dörner Dr. Marion Girod Dr. Luke MacAleese Dr. Cornelius L. Pieterse Dr. Thomas Schlathölter Prof. Dr. Simone Techert Dr. Sadia Bari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12371-12379
We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX+ with M=Fe, Co, Zn) by means of vacuum-ultraviolet (VUV) action spectroscopy in the energy range of 8.5–35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline. The mass spectra and partial ion yields show that photoexcitation of the precursor ions predominantly leads to .CH2COOH radical side-chain losses of the macrocycle with additional methyl radical (.CH3) side-chain losses. Ionization, in contrast, leads to the formation of the intact ionized precursor and various doubly charged fragments which are mostly due to side-chain cleavages. Although statistical fragmentation dominates, we found evidence for non-statistical processes such as new fragments involving for example single and double H2O losses, indicating that different relaxation mechanisms are at play upon photoionization compared to photoexcitation. The measured ionization energies were 9.6±0.2 eV, 9.4±0.2 eV and 9.6±0.2 eV for FePPIX+, CoPPIX+ and ZnPPIX+, respectively. 相似文献
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Domenik Schleier Engelbert Reusch Lisa Lummel Dr. Patrick Hemberger Prof. Dr. Ingo Fischer 《Chemphyschem》2019,20(19):2413-2416
Iodine oxides appear as reactive intermediates in atmospheric chemistry. Here, we investigate IO and HOI by mass-selective threshold photoelectron spectroscopy (ms-TPES), using synchrotron radiation. IO and HOI are generated by photolyzing iodine in the presence of ozone. For both molecules, accurate ionization energies are determined, 9.71±0.02 eV for IO and 9.79±0.02 eV for HOI. The strong spin-spin interaction in the 3Σ− ground state of IO+ leads to an energy splitting into the Ω=0 and Ω=±1 sublevels. Upon ionization, the I−O bond shortens significantly in both molecules; thus, a vibrational progression, assigned to the I−O stretch, is apparent in both spectra. 相似文献
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Engelbert Reusch Dr. Fabian Holzmeier Marius Gerlach Prof. Dr. Ingo Fischer Dr. Patrick Hemberger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(72):16652-16659
The reaction products of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gas phase. Aminomethylpyridines were pyrolyzed to initially produce picolyl radicals (m/z=92). At higher temperatures further thermal reaction products are generated in the pyrolysis reactor. All compounds were identified by mass-selected threshold photoelectron spectroscopy and several hitherto unexplored reactive molecules were characterized. The mechanism for several dissociation pathways was outlined in computations. The spectrum of m/z=91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyrroles with adiabatic ionization energies (IEad) of 7.99 eV (2-ethynyl-1H-pyrrole) and 8.12 eV (3-ethynyl-1H-pyrrole), and two cyclopentadiene carbonitriles with IE′s of 9.14 eV (cyclopenta-1,3-diene-1-carbonitrile) and 9.25 eV (cyclopenta-1,4-diene-1-carbonitrile). A second consecutive hydrogen loss forms the cyanocyclopentadienyl radical with IE′s of 9.07 eV (T0) and 9.21 eV (S1). This compound dissociates further to acetylene and the cyanopropynyl radical (IE=9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargyl were identified in the spectra. Computations indicate that dissociation of picolyl proceeds initially via a resonance-stabilized seven-membered ring. 相似文献
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Fabrizio Innocenti Dr. Marie Eypper Edmond P. F. Lee Dr. Stefano Stranges Dr. Daniel K. W. Mok Dr. Foo‐tim Chau Prof. George C. King Prof. John M. Dyke Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11452-11460
The first photoelectron band of difluorocarbene CF2, has been studied by threshold photoelectron (TPE) spectroscopy. CF2 was prepared by microwave discharge of a flowing mixture of hexafluoropropene, C3F6, and argon. A vibrationally resolved band was observed in which at least twenty‐two components were observed. In the first PE band of CF2, the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF2+ (X?2A1)+e? ← CF2 (X?1A1), there is an increase in the FCF bond angle (by ≈20°) and a decrease in the C? F bond length (by ≈0.7 Å). The adiabatic component was not observed in the experimental TPE spectrum. However, on comparing this spectrum with an ab initio/Franck–Condon simulation of this band, using results from high‐level ab initio calculations, the structure associated with the vibrational components could be assigned. This led to alignment of the experimental TPE spectrum and the computed Franck–Condon envelope, and a determination of the first adiabatic ionization energy of CF2 as (11.362±0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the symmetric stretching mode (ν1′) and symmetric bending mode (ν2′) in CF2+ (X?2A1). 相似文献
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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… 相似文献
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Rahul Narayanan Depanjan Sarkar Prof. R. Graham Cooks Prof. Thalappil Pradeep 《Angewandte Chemie (International ed. in English)》2014,53(23):5936-5940
Ambient ionization is achieved by spraying from a carbon nanotube (CNT)‐impregnated paper surface under the influence of small voltages (≥3 V). Organic molecules give simple high‐quality mass spectra without fragmentation in the positive or negative ion modes. Conventional field ionization is ruled out, and it appears that field emission of microdroplets occurs. Microscopic examination of the CNT paper confirms that the nanoscale features at the paper surface are responsible for the high electric fields. Raman spectra imply substantial current flows in the nanotubes. The performance of this analytical method was demonstrated for a range of volatile and nonvolatile compounds and a variety of matrices. 相似文献
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采用紫外光谱定性定量分析野生植物茅莓主要有效成分黄酮化合物,并对其进行液相色谱-电喷雾质谱联用、薄层色谱原位表面增强拉曼散射研究。液相色谱流动相A:CH3OH,B:H2O 1%乙酸,液相色谱流出时间16.21 m in的化合物为六羟基双氢黄酮醇二聚体形式,分子量640,占总黄酮的91.71%;流出时间19.61 m in的化合物分子量448,为槲皮甙,占总黄酮的8.29%。茅莓总黄酮经聚酰胺薄层色谱板分离,获得两个斑点:R f1=0.14,R f2=0.47;分别制备灰银胶和溴化银光致还原银溶胶表面增强基底,在样品薄层色谱两个斑点原位分别获得2种黄酮化合物的表面增强拉曼光谱,在2种表面增强基底作用下,都能观察到μg量黄酮化合物特征拉曼光谱,并比较了2种色谱分离与指纹检测联用技术。 相似文献
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Prof. Dr. Sergey Yu. Ketkov Dr. Gennady V. Markin Sheng Y. Tzeng Prof. Dr. Wen B. Tzeng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4690-4694
Mass‐analyzed threshold ionization spectra of jet‐cooled [(η6‐PhMe)(η6‐PhH)Cr] and [(η6‐Ph2)(η6‐PhH)Cr] reveal with unprecedented accuracy the effects of methyl and phenyl groups on the electronic structure of bis(η6‐benzene)chromium. These “pure” substituent effects allow quantitative experimental determination of the ionization energy changes caused by the mutual substituent influence in bisarene systems. Two types of such influence have been revealed for the first time in bis(η6‐toluene)chromium. 相似文献
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Fabian Holzmeier Melanie Lang Dr. Patrick Hemberger Prof. Dr. Ingo Fischer 《Chemphyschem》2014,15(16):3489-3492
The ionization of two resonantly stabilized radicals, namely 1‐phenylpropargyl (1PPR) and 3‐phenylpropargyl (3PPR) are reinvestigated applying vacuum ultraviolet synchrotron radiation and threshold photoelectron spectroscopy. Ionization energies of 7.24±0.02 and 7.25±0.01 eV are obtained for 1 and 3PPR respectively, which compare well with ab initio calculations. The quality of the spectra are significantly improved mostly due to the application of a new high‐photon‐flux grating available at the VUV‐beamline of Swiss Light Source. Resolved vibrational features are assigned according to a Franck–Condon approach. 相似文献