郑旭明
光化学反应短时动力学的共振拉曼光谱研究、瞬态物质的时间分辨共振拉曼光谱研究、分子光谱的量子化学计算等方面
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- 姓名:郑旭明
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学术头衔:
博士生导师
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学科领域:
物理化学
- 研究兴趣:光化学反应短时动力学的共振拉曼光谱研究、瞬态物质的时间分辨共振拉曼光谱研究、分子光谱的量子化学计算等方面
1982年2月毕业于浙江工业大学分析化学专业,获工学学士位。1982年3月至今,浙江理工大学任教。2000年任应用化学系教授。1996-2000年香港大学化学系攻读学位,2000年5月获物理化学专业博士学位。现任浙江省化学会理事。2002年7月至今任浙江理工大学理学院副院长。2003年1月当选浙江省人大常委会委员。
近十年来,从事光化学反应动力学研究。在光化学反应短时动力学的共振拉曼光谱研究、瞬态物质的时间分辨共振拉曼光谱研究、分子光谱的量子化学计算等方面积累了丰富的经验,取得了重要的研究成果,例如,采用时间分辨共振拉曼光谱技术和量子化学计算方法,表征了十几种多碘溴甲烷在溶液相光解中产生的瞬态物质的结构,研究了它们的结构与性能的关系,解决了国际上有关多卤代甲烷溶液相光化学反应动力学研究中长期悬而未决的难题,提出了Simmons- Smith反应的机理。在J. Am. Chem. Soc., J. Chem. Phys., J. Phys. Chem., Chem. Phys. Lett., 和高等学校化学学报等国际国内期刊上共发表SCI论文34篇。回国后,作为项目主持人完成教育部优秀青年教师资助计划项目和浙江省自然科学基金项目等省部级项目4项。建成“时间分辨共振拉曼光谱研究实验室”。目前正承担国家自然科学基金面上项目1项、浙江省高校中青年学科带头人重点资助项目1项。
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郑旭明, Xin-Ming Zhu†, Shu-Qiang Zhang†, Xuming Zheng, *, †, and David Lee Phillips*, ‡
J. Phys. Chem. A 2005, 109, 3086~3093,-0001,():
-1年11月30日
Resonance Raman spectra were obtained for nitrobenzene in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) band absorption spectrum. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal NO2 symmetric stretch mode (v11), the nominal benzene ring stretch mode (v7), accompanied by a moderate degree of motion along the nominal ONO symmetry bend/benzene ring stretch mode (v23), the nominal C-N stretch/benzene ring breathing mode (
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郑旭明, Xuming Zheng, *, ‡, Yun-Liang Li, §, and David Lee Phillips*
J. Phys. Chem. A 2004, 108, 8032~8039,-0001,():
-1年11月30日
Resonance Raman spectra were obtained for cyclopropyl iodide in cyclohexane solution with excitation wavelengths in resonance with the A-band absorption spectrum. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal C-I stretch and nominal C-C-I deformation normal modes accompanied by moderate motion along the nominal cyclopropyl ring breathing and ring deformation normal modes. A preliminary resonance Raman intensity analysis was done, and the results for cyclopropyl iodide were compared to previously reported results for several cyclic and noncyclic alkyl iodides.
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郑旭明, Xuming Zheng, Wai Ming Kwok, ‡, and David Lee Phillips*
J. Phys. Chem. A 2000, 104, 10464~10470,-0001,():
-1年11月30日
We have obtained A-band resonance Raman spectra of dibromomethane in the gas and solution phase and nanosecond time-resolved resonance Raman spectra of dibromomethane photoproducts. The A-band resonance Raman spectra suggest the short-time dynamics are similar to other dihalomethanes that are known to have direct photodissociation reactions in the gas phase. Several power dependent A-band resonance Raman bands were tentatively assigned to the C-Br stretch overtone progression of the CH2Br radical which has a strong absorption band that is coincident with the A-band resonance Raman excitation wavelength. Two-color nanosecond time-resolved resonance Raman spectra (266.0nm pump/341.5nm probe) were obtained and comparison of the vibrational frequencies to the results for density functional theory calculations indicate that the iso-CH2Br-Br species is mainly responsible for the transient photoproduct absorption band 360nm. Our preliminary results for A-band photoexcitation of dibromomethane in conjunction with previously reported diiodomethane results suggest that solvation effects (probably via recombination of the CH2Br and Br fragments within a solvent cage) lead to noticeable production of the isodibromomethane photoisomerization photoproduct observed in the nanosecond time-resolved resonance Raman spectra.
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郑旭明, Xuming Zheng, and David Lee Phillips*
J. Phys. Chem. A 2000, 104, 6880~6886,-0001,():
-1年11月30日
We report transient resonance Raman experiments that identify isodiiodomethane as the photoproduct responsible for the 385 nm absorption band observed following ultraviolet excitation of diiodomethane in liquid solutions. Comparison with previously reported gas-phase experiments and solution-phase resonance Raman and femtosecond transient absorption results suggest that solvation leads to appreciable production of the isodiiodomethane (H2C-I-I) photoproduct via the interaction of the initially formed CH2I and I fragments with the solvent cage. The isodiiodomethane photoproduct is likely the species or an intermediate to the species that reacts with alkenes in cyclopropanation reactions that use ultraviolet excitation of diiodomethane in liquids.
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【期刊论文】Ab Initio Investigation of XCH2CH2 and XCHCH3 Radicals (X=F, Cl, Br)
郑旭明, Xuming Zheng, and David Lee Phillips*
J. Phys. Chem. A 2000, 104, 1030~1038,-0001,():
-1年11月30日
We have done ab initio calculations to find the equilibrium geometries, rotational/inversion barriers, and harmonic vibrational frequencies of several haloethyl radicals (XCH2CH2 and XCHCH3 where X=F, Cl, Br). One equilibrium and two transition conformations for XCH2CH2 (X=Cl, Br) and XCHCH3 (X=F, Cl, Br) were found on the calculated B3LYP/6-311++G(3df,3pd) potential energy surface. We discuss the effects of the halo substituents on the haloethyl radicals investigated. The C-X bonds of the equilibrium
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郑旭明, Xuming Zheng, a), Cheong Wan Lee, Yun-Liang Li, Wei-Hai Fang, b), and David Lee Phillipsc)
J. Chem. Phys., Vol. 113, No.17, 1 November 2000,-0001,():
-1年11月30日
We report transient resonance Raman spectra and density functional theory calculations for the photoproducts produced after ultraviolet excitation of CHBr2Cl and CCl3Br in cyclohexane solution. Comparison of the computed vibrational frequencies to the experimental Raman frequencies revealed that the iso-CHBrCl-Br and iso-CHClBr-Br species are mainly responsible for the transient resonance Raman spectrum observed following ultraviolet excitation of CHBr2Cl. Similar comparisons for CCl3Br showed the iso-CCl2Cl-Br species is mainly responsible for the transient resonance Raman spectrum observed following ultraviolet excitation of CCl3Br. Additional density functional theory computations were done to examine the chemical reactions of iso-CH2Br-Cl and iso-CH2Cl-Br with ethylene to give cyclopropane and Br-Cl product. We briefly discuss the possibility for release of reactive halogens into the atmosphere via the photochemical and chemical reactions of iso-polyhalomethane molecules formed after ultraviolet excitation of polyhalomethanes in condensed phase environments.
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郑旭明, Wai Ming Kwok and Chensheng Ma, Anthony W. Parker, David Phillips, Michael Towrie, and Pavel Matousek, David Lee Phillipsa)
J. Chem. Phys., Vol. 114, No.19, 15 May 2001,-0001,():
-1年11月30日
We report a preliminary picosecond Stokes and anti-Stokes time-resolved resonance Raman ~267nm pump and 400nm probe excitation wavelengths! investigation of the initial formation and vibrational cooling of the iso-CH2I-I photoproduct species produced after ultraviolet excitation of diiodomethane in room temperature solutions. A comparison of the picosecond resonance Raman spectra with previously reported nanosecond transient resonance Raman spectra and density functional theory computations shows that the iso-CH2I–I photoproduct species is predominantly responsible for the ;385 nm transient absorption band observed from several picoseconds to nanoseconds after ultraviolet excitation of diiodomethane in the solution phase. Similar results were obtained in both nonpolar solution ~cyclohexane solvent! and polar solution~ acetonitrile! solvent. The picosecond resonance Raman spectra confirm that the iso-CH2I-I photoproduct species is formed vibrationally hot within several picoseconds and then subsequently undergoes vibrational cooling on the 4-50ps time scale. This is consistent with the absorption bands changes occurring over similar times in a recent femtosecond transient absorption study. We discuss a possible qualitative scenario for the formation of the iso-CH2I-I species that is in agreement with the available gas phase experimental results for the ultraviolet photodissociation reaction of diiodomethane and gas phase collisional deactivation studies of the CH2I radical. The proposed hypothesis is consistent with the lack of distinct resonance Raman bands in the first few picoseconds of our solution phase spectra of the iso-CH2I-I photoproduct as well as previously reported femtosecond transient absorption bands that are broad and weak in the 300-500nm region over the 0.3-3ps time scale.
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郑旭明, Xuming Zheng, Wei-Hai Fang, a), and David Lee Phillipsb)
J. Chem Phys. Vol. 113, No.24 , 22 Decamber 2000,-0001,():
-1年11月30日
We report additional transient resonance Raman spectra and density functional theory computations for the products formed following ultraviolet photoexcitation of solution phase polyhalomethanes containing bromine and/or iodine atoms. We show that the iso-polyhalomethane photoproduct is responsible for the intense transient absorption band observed in the 350-470nm region after ultraviolet excitation of pnlyhalomethanes in the solutinn phase. We examine the trends and correlation in the density functional theory optimized geometry and intense electronic absorption transition in the 350-470 nm region for the iso-polyhalomethanes containing bromine and/or iodine atoms. We explore the chemical reactivity of the iso-polyhalomethane species using density functional theory computations for the reaction of iso-CH2-Br-Br with ethylene as an example. Our results and comparison with experimental data in the literature indicate that the iso-polyhalomethane species is most likely the methylene transfer agent in the cyclopropanation reactions of olefins using nltraviolet photoexcitation of polyhalomethanes in the solution phase. We briefly discuss the possibilitv that the photochemistry and chemistry of the iso-polyhalomethanes may give significant release of reactive halogens to the atmosphere.
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郑旭明, Xuming Zheng. and David Lee Phillipsa)
J. Chem. Phys., Vol. 113, No.8, 22 August 2000,-0001,():
-1年11月30日
We present nanosecond transient resonance Raman experiments that investigate the photoproduct species formed following A-band and B-band excitation of bromoiodomethane in room temperature cyclohexane solutions. Density functional theory calculations were also performed for several species that have been proposed as photoproducts for photodissociation of bromoiodomethane in the condensed phase. Comparison of the experimental resonance Raman spectra to density functional theory computational results and results for the closely related iso-CH2I-I and iso-CH2Br-Br species demonstrated that the iso-CH2I–Br species is mainly responsible for a transient absorption spectrum that appears after either A-band or B-band photoexcitation of bromoiodomethane in cyclohexane solution. This is in contrast to previous results for low temperature (12 K) solids where mainly the iso-CH2Br-I species was observed following A-band photoexcitation of bromoiodomethane. Further density functional theory computational results indicate that the iso CH2I–Br species is noticeably more stable than the iso-CH2Br-I species by about 4.1kcal/mol. This suggests that although both iso-CH2I–Br and iso-CH2Br–I species may be initially produced following ultraviolet excitation of bromoiodomethane in cyclohexane solution, only the more stable isomer has a sufficiently long lifetime to be observed in our nanosecond time-scale transient resonance Raman experiments. We compare results for the bromoiodomethane ultraviolet photodissociation/photoisomerization reactions in the condensed phase to those of the closely related diiodomethane system and discuss a probable mechanism for the formation of the iso-bromoiodomethane species in the condensed phase.
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郑旭明, Xuming Zheng, Cheong Wan Lee, and David Lee Phillipsa)
J. Chem. Phys., Vol. 111, No.24, 22 December 1999,-0001,():
-1年11月30日
We have obtained resonance Raman spectra of iodocyclopentane in cyclohexane solution at three excitation wavelengths resonant with the A-band absorption. The A-band resonance Raman spectral bands can be assigned to fundamentals, overtones, and combination bands of seven axial conformer and eight equatorial conformer Franck–Condon active modes. The resonance Raman and absorption cross sections were simultaneously simulated using wave packet calculations and a simple model. The best fit parameters of the simulations and the normal mode descriptions were used to determine the A-band short-time photodissociation dynamics of the axial and equatorial conformers of iodocyclopentane. The axial and equatorial conformers exhibit noticeably different short-time photodissociation dynamics that suggest that the C-I bond cleavage process is conformation dependent. The axial conformer short-time photodissociation dynamics have larger changes in the carbon-carbon stretch and three carbon atombending motions as well as the torsional motion about the a and b carbon atom bond. The CCI bending motions for the axial and equatorial conformers of iodocyclopentane as well as previously reported results for the equatorial conformer of iodocyclohexane are significantly smaller than CCI bending motions found for most noncyclic iodoalkanes examined so far. This suggests that the cyclic backbone restricts the initial motion of the C-I bond cleavage along the CCI bend in iodocycloalkanes compared to the noncyclic iodoalkanes.
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