In this letter, the development of an electron momentum spectrometer, which is the first in China, has been described shortly, and using this spectrometer, the experimental results on the electron momentum spectroscop...In this letter, the development of an electron momentum spectrometer, which is the first in China, has been described shortly, and using this spectrometer, the experimental results on the electron momentum spectroscopy of helium were reported.展开更多
The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-o...The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-orbital relativistic DFT-B3LYP calculations. The experimental momentum profiles of the outer valence orbitals obtained with the impact energies of 1200 eV and 2400 eV were compared with various theoretical calculation results. The relativistic calculations could provide better descriptions for the experimental momentum distributions than the non-relativistic ones. Moreover, a new ordering of orbitals 10tlu, 3t2g, and 7eg, i.e., 10t_lu 〈 3t_2g 〈7e_g 〈10a_lg, is established in this work.展开更多
The electronic structure of nitrogen trifluoride was investigated by combining the high-resolution electron momentum spectroscopy with the high-level calculations. The experimental binding energy spectra and the momen...The electronic structure of nitrogen trifluoride was investigated by combining the high-resolution electron momentum spectroscopy with the high-level calculations. The experimental binding energy spectra and the momentum distributions of each orbital were compared with the results of Hartree-Fock, density functional theory （DFT）, and symmetry-adapted- cluster configuration-interaction （SAC-CI） methods. SAC-CI and DFT-B3LYP with the aug-cc-pVTZ basis set can well reproduce the binding energy spectra and the observed momentum distributions of the valence orbitals except 1 a2 and 4e orbitals. It was found that the calculated momentum distributions using DFT-B3LYP are even better than those using the high-level SAC-CI method.展开更多
Electronic states of CF2Cl2 （dichlorodifluoromethane, Freon 12） have been studied using a new type of electron momentum spectrometer with a very high efficiency at an impact energy of 1200 eV plus binding energy. Th...Electronic states of CF2Cl2 （dichlorodifluoromethane, Freon 12） have been studied using a new type of electron momentum spectrometer with a very high efficiency at an impact energy of 1200 eV plus binding energy. The experimental electron momentum profiles are compared with the density functional theory （DFT） and Hartree-Fock （HF） calculations. The relationship between orbital assignments in different coordinate systems is discussed. A new method of difference analysis based on the new type of electron momentum spectrometer is used to clarify the ambiguities regarding the orbital ordering.展开更多
The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A...The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A 98042705(2018)].The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively,indicating that the vibrational motion in benzene molecule has noticeable influence on its electron momentum distributions.展开更多
We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV ...We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV by a binary （e, 2e） spectrometer. The experimental momentum profiles of the HOMO orbital are compared with the theoretical momentum distribution calculated using the Hartree Fock and density functional theory methods with various basis sets. However, none of these calculations gives a completely satisfactory description of the momentum distributions of the HOMO 762. The inadequacy of the calculations could result in the intensity difference of the second maximum at p-1.2a.u. between the experiment and the theory. The discrepancy between experimental and theoretical data in the low-momentum region is explained with the distorted wave effect.展开更多
Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow＇s work titled ＂Is it time to retire the hybrid atomic orbital？＂ [J. Chem. Educ. 88, 860 （2011）]. To c...Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow＇s work titled ＂Is it time to retire the hybrid atomic orbital？＂ [J. Chem. Educ. 88, 860 （2011）]. To clarify the issue, we assess the delocalized and localized molecular orbitals from an experimental view using electron momentum spectroscopy. The delocalized and localized molecular orbitals based on various theoretical models for CH4, NH3, and H20 are compared with the experimental momentum distributions. Our results show that the delocalized molecular orbitals rather than the localized ones can give a direct interpretation of the experimental （e, 2e） results.展开更多
Orbital responses to methyl sites in CnH2n＋2 （n = 1-6） are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-p...Orbital responses to methyl sites in CnH2n＋2 （n = 1-6） are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital （HOMO） investigations indicate the p- electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space （P 〈 0.50 a.u.）. Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.展开更多
The electron momentum spectra of outer valence orbitals 2e and 4a 1 of trichlorofluoromethane have been measured by binary (e, 2e) electron momentum spectroscopy at impact energy of 1200 eV plus binding energy and sym...The electron momentum spectra of outer valence orbitals 2e and 4a 1 of trichlorofluoromethane have been measured by binary (e, 2e) electron momentum spectroscopy at impact energy of 1200 eV plus binding energy and symmetric non-coplanar geometry. The experimental momentum profiles of these two orbitals are compared with theoretical momentum profiles calculated by Hartree-Fock (HF) and Density Functional Theory (DFT) using different-sized basis sets.Generally, DFT calculations reproduce the experimental results better than HF calculations. The characters of 2e and 4a 1 orbitals are also discussed and shows that 2e is predominantly fluorine lone pair orbital while 4a 1 C-F bonding orbital.展开更多
The electron momentum spectroscopy of the inner valence orbitals 3a 1 and 2b 2 of methylene fluoride was studied by electron momentum spectroscopy(EMS). The experiment was performed using a high resolution(ΔE=1.15 eV...The electron momentum spectroscopy of the inner valence orbitals 3a 1 and 2b 2 of methylene fluoride was studied by electron momentum spectroscopy(EMS). The experiment was performed using a high resolution(ΔE=1.15 eV FWHM, Δp=0.1 a.u.)(e,2e) EMS spectrometer. The experimental momentum profiles of these two orbitals are compared with those calculated by Hartree-Fork method and Density Functional Theory.展开更多
文摘In this letter, the development of an electron momentum spectrometer, which is the first in China, has been described shortly, and using this spectrometer, the experimental results on the electron momentum spectroscopy of helium were reported.
基金supported by the National Natural Science Foundation of China(Grant Nos.11074144,10874097,and 10704046)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20070003146)
文摘The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-orbital relativistic DFT-B3LYP calculations. The experimental momentum profiles of the outer valence orbitals obtained with the impact energies of 1200 eV and 2400 eV were compared with various theoretical calculation results. The relativistic calculations could provide better descriptions for the experimental momentum distributions than the non-relativistic ones. Moreover, a new ordering of orbitals 10tlu, 3t2g, and 7eg, i.e., 10t_lu 〈 3t_2g 〈7e_g 〈10a_lg, is established in this work.
基金supported by the National Natural Science Foundation of China(Grant No.11174175)the Tsinghua University Initiative Scientific Research Program,China
文摘The electronic structure of nitrogen trifluoride was investigated by combining the high-resolution electron momentum spectroscopy with the high-level calculations. The experimental binding energy spectra and the momentum distributions of each orbital were compared with the results of Hartree-Fock, density functional theory （DFT）, and symmetry-adapted- cluster configuration-interaction （SAC-CI） methods. SAC-CI and DFT-B3LYP with the aug-cc-pVTZ basis set can well reproduce the binding energy spectra and the observed momentum distributions of the valence orbitals except 1 a2 and 4e orbitals. It was found that the calculated momentum distributions using DFT-B3LYP are even better than those using the high-level SAC-CI method.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 19854002, 19774037 and 10274040） and the Research Fund for the Doctorate Program of Higher Education （Grant No 1999000327）.
文摘Electronic states of CF2Cl2 （dichlorodifluoromethane, Freon 12） have been studied using a new type of electron momentum spectrometer with a very high efficiency at an impact energy of 1200 eV plus binding energy. The experimental electron momentum profiles are compared with the density functional theory （DFT） and Hartree-Fock （HF） calculations. The relationship between orbital assignments in different coordinate systems is discussed. A new method of difference analysis based on the new type of electron momentum spectrometer is used to clarify the ambiguities regarding the orbital ordering.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300).
文摘The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A 98042705(2018)].The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively,indicating that the vibrational motion in benzene molecule has noticeable influence on its electron momentum distributions.
基金Supported by the National Natural Science Foundation of China under Grant No 10575062, and the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20050003084.
文摘We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV by a binary （e, 2e） spectrometer. The experimental momentum profiles of the HOMO orbital are compared with the theoretical momentum distribution calculated using the Hartree Fock and density functional theory methods with various basis sets. However, none of these calculations gives a completely satisfactory description of the momentum distributions of the HOMO 762. The inadequacy of the calculations could result in the intensity difference of the second maximum at p-1.2a.u. between the experiment and the theory. The discrepancy between experimental and theoretical data in the low-momentum region is explained with the distorted wave effect.
基金supported by the National Natural Science Foundation of China(Grant No.11174175)the Tsinghua University Initiative Scientific Research Program,China
文摘Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow＇s work titled ＂Is it time to retire the hybrid atomic orbital？＂ [J. Chem. Educ. 88, 860 （2011）]. To clarify the issue, we assess the delocalized and localized molecular orbitals from an experimental view using electron momentum spectroscopy. The delocalized and localized molecular orbitals based on various theoretical models for CH4, NH3, and H20 are compared with the experimental momentum distributions. Our results show that the delocalized molecular orbitals rather than the localized ones can give a direct interpretation of the experimental （e, 2e） results.
基金supported by the National Natural Science Foundation of China (Grant Nos.10974139,11104247,and 11176020)
文摘Orbital responses to methyl sites in CnH2n＋2 （n = 1-6） are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital （HOMO） investigations indicate the p- electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space （P 〈 0.50 a.u.）. Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.
基金supported by the National Natural Science Foundation of China(10676025,10574096)China Scholarship Council(CSC)Science-Technology Foundation for Young Scientist of Sichuan Province,China(09ZQ026-049)~~
文摘The electron momentum spectra of outer valence orbitals 2e and 4a 1 of trichlorofluoromethane have been measured by binary (e, 2e) electron momentum spectroscopy at impact energy of 1200 eV plus binding energy and symmetric non-coplanar geometry. The experimental momentum profiles of these two orbitals are compared with theoretical momentum profiles calculated by Hartree-Fock (HF) and Density Functional Theory (DFT) using different-sized basis sets.Generally, DFT calculations reproduce the experimental results better than HF calculations. The characters of 2e and 4a 1 orbitals are also discussed and shows that 2e is predominantly fluorine lone pair orbital while 4a 1 C-F bonding orbital.
文摘The electron momentum spectroscopy of the inner valence orbitals 3a 1 and 2b 2 of methylene fluoride was studied by electron momentum spectroscopy(EMS). The experiment was performed using a high resolution(ΔE=1.15 eV FWHM, Δp=0.1 a.u.)(e,2e) EMS spectrometer. The experimental momentum profiles of these two orbitals are compared with those calculated by Hartree-Fork method and Density Functional Theory.
