B-X and C-X Band Systems of CuCl Revisited: Laser-induced Fluorescence Study in 465−490 nm

We have reinvestigated the B-X and C-X band systems of CuCl by recording the laser-induced fluorescence excitation spectra in 20400?21800 cm^?1. The rotational analyses in Hund’s case (a) revealed unambiguously a singlet-to-singlet transition nature. The radiative lifetimes were measured to be 4.670 and 4.667 μs, respectively, which are much longer than that expected for a pure singlet of CuCl. This implies that the fluorescence mechanism in the B or C band systems lies in the mixing of the singlets (¹Пand ¹∑⁺) and triplets (³П_0,1,2) and that the two excited states observed in our experiment might be the singlets that have been strongly “contaminated” by their triplet neighbors.     

Magnetic-Bottle and Velocity-Map Imaging Photoelectron Spectroscopy of APS- (A=C14H10 or Anthracene): Electron Structure,Spin-Orbit Coupling of APS·, and Dipole-Bound State of APS-

Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS^-(A=C₁₄H₁₀ or anthracene) were generated via electrospray ionization, and characterized by magnetic-bottle photoelectron spectroscopy, velocity-map imaging (VMI) photoelectron spectroscopy, and quantum chemical calculations. The electron affinity (EA) and spin-orbit (SO) splitting of the APS^· radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA=(2.62±0.05) eV and SO splitting=(43±7) meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy (eKE) of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31++G(d, p) calculations indicate APS^· has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.     

Mass Spectrometric and Photoelectron Spectroscopic Studies of Zirconium Oxide Molecular and Cluster Anions

We present a preliminary report on our mass spectrometric and photoelectron spectroscopic studies of zirconium oxide molecular and cluster anions using a newly built laser vaporization/time-of-flight/magnetic bottle, negative ion photoelectron spectrometer. This work was motivated in part by evidence which suggests that zirconium dioxide catalyzes the radiolysis of interfacial water. We present our mass spectrometric observations of oxygen-rich zirconium oxide cluster anions and our photoelectron spectra of ZrO^– and ZrO ₂ ^– . From the photoelectron spectrum of ZrO^–, the adiabatic electron affinity of ZrO was determined to be 1.3±0.3 eV, and from this value, the dissociation energy of ZrO^– (into Zr and O^–) was found to be 7.8±0.3 eV. From the photoelectron spectrum of ZrO₂, the adiabatic electron affinity of ZrO₂ was determined to be 1.8±0.4 eV.     

荧光色散谱对FeS(X5△)振动常数的实验确认

Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X⁵△ electronic state were obtained by directly mapping the ground-state vibrational levels up to v″=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS(X⁵△) (518±5 cm-1) agrees well with that reported in a recent PES measurement (520±30 cm-1) [J. Phys. Chem. A 107, 2821 (2003)] which is the only one prior experimental vibrational frequency value for the ⁵△ state of FeS. Careful comparisons of our experimental results and those documented in the literature (mainly from theoretical predictions) suggest that the ground state of FeS is ⁵△ state.     

Electron beam reduction of cubic Y-doped ZrO2(100): A study by X-ray photoelectron spectroscopy

Electron beam reduction of cubic Y(III)-doped ZrO₂(100) has been studied by X-ray photoelectron spectroscopy. In the initial stages of irradiation with 2-keV electrons oxygen loss is accompanied by specific reduction of Zr(IV) to Zr(0) without concomitant reduction of Y(III). The cross section for oxygen desorption is estimated to be 3.9 × 10⁻²⁰ cm². Surface stoichiometry is restored by argon-ion bombardment.     

The structure of p-chlorophenol and barrier to internal OH rotation in the S1-state

The structure and barrier to internal rotation of 4-chlorophenol in the ground state and the electronically excited S₁-state has been examined by rotationally resolved laser induced fluorescence spectroscopy of 4-³⁵Cl-phenol, 4-³⁷Cl-phenol, 4-³⁵Cl-phenol-d₁, and 4-³⁷Cl-phenol-d₁. The overlapping spectra have been assigned simultaneously using a genetic algorithm approach. The rotationally resolved spectrum of the electronic origin of 4-chlorophenol is comprised of two subbands, which are split by 60 MHz due to the internal rotation of the hydroxy group. The torsional barrier in the electronically excited state could be estimated to be 1400 cm⁻¹, only about 250 cm⁻¹ higher than in the ground state. The CCl bond lengths decreases by approximately 6 pm upon electronic excitation and the aromatic ring is distorted quinoidally.     

In situ Nanomechanical Research on Large-Scale Plastic Deformation of Individual Ultrathin Multi-walled Carbon Nanotube

Carbon nanotubes are a promising candidate for the application of flexible electronics due to the ultrahigh intrinsic conductivity and excellent mechanical flexibility. In the present work,the morphology of the ultrathin (diameter<20 nm) multi-walled carbon nanotubes (MWCNTs) under an axial compression was investigated by using in-situ transmission electron microscopy. Moreover, the overall dynamic deformation processes and the force-displacement (F-D) curves of the MWCNTs were also examined. Interestingly, the MWCNTs almost restored their original morphology after 15 loading-unloading cycles. The deformation and recovery process indicate that the MWCNTs are flexible and exhibit excellent durability against compression. The Young’s modulus of the MWCNTs is estimated with the value of ∽0.655 TPa derived from the F-D curves fitting. Our results suggest that the ultrathin carbon nanotube structures may have great application potentials in flexible devices.     

Tcn and Tcn@C70 Endohedral Metalofullerenes: ab initio Spin-density-functional Calculations

Ab initio spin-density-functional calculations have been performed to study the equilibrium structural, electronic, and magnetic properties of Tcn and Tc_n@C₇₀ endohedral metalofullerenes. Our results indicate that C₇₀ can encapsulate Tcn clusters with up to n=9 atoms. Except n=2, the formation of Tc_n@C₇₀ endohedral metalofullerenes is predicted to be exothermic when n≤5, while the encapsulation process becomes increasingly endothermic beyond n=5. When encapsulating into the C₇₀ cage, the geometries as well as electronic structures of the Tc cluster undergo comparative changes. Especially, compared to the isolated Tcn clusters, the total magnetic moments of Tc_n@C₇₀ reduce significantly. The analyses of the orbital population, Hirshfeld population and density of states show that electrons transfer from the Tc cluster to the carbon cage through the Tc-C efficient hybridization, which is responsible for such reduction of the whole magnetism.     

Improved Calculation of Vibrational Energy Levels in F2 Molecule using the RKR Method

The potential energy curves of the ground state X²∑⁺_g of the fluorine molecule have been ac-curately reconstructed employing the Ryderg-Klein-Rees (RKR) method extrapolated by a Hulburt and Hirschfeler potential function for longer internuclear distances. Solving the cor-responding radial one-dimensional Schr?dinger equation of nuclear motion yields 22 bound vibrational levels above v=0. The comparison of these theoretical levels with the experimen-tal data yields a mean absolute deviation of about 7.6 cm^-1 over the 23 levels. The highest vibrational level energy obtained using this method is 13308.16 cm?1 and the relative de-viation compared with the experimental datum of 13408.49 cm^-1 is only 0.74%. The value from our method is much closer and more accurate than the value obtained by the quantum mechanical ab initio method by Bytautas. The reported agreement of the vibrational levels and dissociation energy with experiment is contingent upon the potential energy curve of the F₂ ground state.     

Electron Affinities of the Early Lanthanide Monoxide Molecules

The photoelectron imagings of LaO^-, CeO^-, PrO^-, and NdO^- at 1064 nm are reported. The well resolved photoelectron spectra allow the electron a±nities to be determined as 0.99(1) eV for LaO, 1.00(1) eV for CeO, 1.00(1) eV for PrO, and 1.01(1) eV for NdO, respectively. Density functional calculations and natural atomic orbital analyses show that the 4f electrons tend to be localized and suffer little from the charge states of the molecules. The photodetached electron mainly originates from the 6s orbital of the metals. The ligand field theory with the δ=2 assumption is still an effective method to analyze the ground states of the neutral and anionic lanthanide monoxides.     

Collinear Velocity-map Photoelectron Imaging Spectrometer for Cluster Anions

We describe a collinear velocity-map photoelectron imaging spectrometer, which combines a Wiley-McLaren time-of-flight mass analyzer with a dual-valve laser vaporization source for investigating size-selected cluster and reaction intermediate anions. To generate the reaction anions conveniently, two pulsed valves and a reaction channel are employed instead of premixing carrier gas. The collinear photoelectron imaging spectrometer adopts modified velocity-map electrostatic lens, and provides kinetic energy resolution better than 3%. The performance of the instrument is demonstrated on the photodetachment of Si₄^- at 532 and 355 nm, and Si₃C^- at 532 nm, respectively. In both cases, photoelectron spectra and anisotropy parameters are obtained from the images. For Si₄^-, the spectra show two well-resolved vibrational progressions which correspond to the ground state and the first excited state of the neutral Si₄ with peak spacing of 330 and 312 cm^-1, respectively. Preliminary results suggest that the apparatus is a powerful tool for characterizing the electronic structure and photodetachment dynamics of cluster anions.     

Ab initio valence bond calculations. VII. HF,HF+, and H2F+

Ab initio valence bond calculations for the ground and excited states of HF and HF⁺ are presented. Total energies, equilibrium geometries, dissociation energies, dipole moments, and spectroscopic constants for HF and HF⁺ have been calculated. The photoelectron spectrum of HF has been examined and interpreted by means of the valence bond formalism. The ground state of the protonated species H₂F⁺ has been investigated.     

A study of aluminium monofluoride and aluminium trifluoride by high-temperature photoelectron spectroscopy

The Hel photoelectron spectrum of gaseous AIF(X¹Σ⁺) has been recorded and the first three cationic states have been assigned with the aid of PNO/CEPA calculations. The first band shows vibrational structure and analysis of the component separations and relative intensitives leads to values of ω_c = 1040 ± 40 cm^?1 and r_c = 1.59 ± 0.01 Å in the AIF⁺ (X²Σ⁺) state; the corresponding theoretical values are 960 cm^?1 and 1.60 Å respectively. The first adiabatic ionization potential, 9.73 ± 0.01 eV, allows a determination of the quantum defect, δ, in a number of previously observed Rydberg states of AIF. The Hel photoelectron spectrum of gaseous AIF₃ has also been obtained. It is assigned on the basis of ab initio molecular orbital calculations and comparison with the corresponding BF₃ spectrum.     

Ultrafast Dynamics of Water Molecules Excited to Electronic F States: A Time-Resolved Photoelectron Spectroscopy Study

The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F₁A₁ and F₁B₁ states of H₂O (D₂O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F₁A₁ state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F₁B₁ state decays through the F₁A₁ state via Coriolis interaction.     

Synthesis,X-ray studies,spectroscopic investigation,and DFT calculations of [ReBr<Subscript>3</Subscript>(dppt)(OPPh<Subscript>3</Subscript>)]

The reaction of [ReOBr₃(PPh₃)₂] with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) has been examined and [ReBr₃(dppt)(OPPh₃)] has been obtained. It was characterised by IR, UV–Vis spectroscopy, magnetic measurements, and X-ray crystallography. The electronic structure of [ReBr₃(dppt)(OPPh₃)] has been studied by DFT/B3LYP level calculations, and TDDFT calculations were employed for discussion of its electronic spectrum in more detail. The magnetic behavior is characteristic of mononuclear complexes with d⁴ low-spin octahedral Re(III) complexes (³T_1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state.     

HCF(X~1A’)+SO2反应的动力学研究

用激光光解-激光诱导荧光方法研究了室温下(T＝293 K) HCF(X^~1A^’)自由基与SO₂分子的反应动力学. 实验中HCF(X^~1A^’)自由基是由213 nm激光光解HCFBr₂产生的, 用激光诱导荧光(LIF)检测HCF(X^~1A^’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k＝(1.81±0.15)×10^－12 cm³&#8226;molecule^－1&#8226;s^－1, 体系总压为1862 Pa. 高精度理论计算表明, HCF(X^~1A^’)和SO₂分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好.     

基态N2O－的势能函数研究

以6-311＋＋G(3df, 3pd)为基函数, 采用密度泛函理论的B3LYP方法对N₂O^－分子体系的结构进行了优化计算. 结果表明N₂O^－分子最稳态为C_s构型, 电子组态为²A', 平衡核间距R_N—N＝0.11873 nm, R_N—O＝0.13012 nm, 键角∠NNO＝133.94448°, 离解能D_e＝10.3857 eV, 基态简正振动频率: 弯曲振动频率ν₁＝656.7488 cm^－1, 对称伸缩振动频率ν₂＝998.1562 cm^－1, 反对称伸缩振动频率ν₃＝1684.3093 cm^－1. 并用多体展式理论方法推导出了基态N₂O^－分子的分析势能函数, 其等值势能图准确地再现了N₂O^－分子的结构特征和离解能.     

Radiative decay of vibrationally excited CH2-

We have observed the presence of vibrationally excited CH₂^- created in a discharge, by measuring the photodetachment from CH₂^- as it radiatively relaxes in a high vacuum ion trap. We used a tunable IR laser to produce photons with energies above and below the expected threshold for removing an electron from the ground state. The time dependence of the photodetachment is consistent with the electron affinity of 5250 cm^-1 (0.65 eV) obtained by Sears and Bunker for the ground state X?³B₁ methylene. We have tentatively assigned radiative lifetimes for the excited bending vibrations of CH₂^-:600 ±300 msec for v₂ = 1,80±40msec for v₂ = 2, and 10± 5 msec for v₂ = 3.     

CO2 Activation by Zr+ and ZrO+ in Gas Phase

The gas-phase reduction of carbon dioxide to carbon monoxide, induced by Zr⁺ and ZrO⁺ catalysts, was investigated at density functional level of theory. Calculations were carried out using both hybrid and pure exchange-correlation functionals in order to reproduce adequately the energetic gap between the Zr^{+ 4}F and ²D electronic states and experimental reaction heats. In agreement with a guided ion beam tandem mass spectrometer study, we have found that carbon dioxide activation by Zr⁺ presents a spin-forbidden mechanism because of a spin inversion process occurring during reaction in the rate- determining step. ZrO⁺ interacts with CO₂ through two possible pathways both endothermic: formation of ZrO ₂ ⁺ and CO products is less unfavourable. Information about ground and excited states of ZrO⁺ and ZrO ₂ ⁺ oxides and bond dissociation energies of species present on the reaction paths was also given.     

Electronic states of Al2

Ab initio multi-configuration self-consistent field and first-order configuration interaction (FOCI) calculations in an extended basis set have been carried out for the lower energy electronic states of Al₂. The ten core electrons of each Al atom were replaced by an accurate compact effective core potential. The FOCI calculated T_o value for the ³Σ_g^?-³Σ_u^? transition agrees with the experimentally observed emission band to within 90 cm^?1. ³Π_u is calculated to be the electronic ground state of Al₂. Based on FOCI energies and qualitative intensity arguments, the reported optical absorption spectrum of matrix isolated Al₂ also agrees best with a ³Π_u ground state. The ³Σ_g^?1 state is calculated (T_e) at only 324 cm^?1 above the ³Π_u state, and the ¹ΣE_g⁺ state is predicted to lie higher.