Microwave spectrum of methyl fluoride in excited vibrational states: Coriolis interaction and anomalous l-doubling transitions

The microwave spectrum of CD₃F in the v₂ = 1, v₃ = 1, v₅ = 1, and v₆ = 1 states was observed, including the direct l-doubling transitions in the v₅ = 1 and v₆ = 1 states. The Coriolis interaction between the v₂ = 1 and v₅ = 1 states was analyzed in detail. An anomaly in the Stark effect was noticed in some of the direct l-doubling transitions in the v₆ = 1 states, and was explained in terms of accidental degeneracy between the Kl₅ = 1 and the Kl₅ = ? 2 levels. Molecular constants associated with the vibrational and rotational motions were determined through an analysis of these spectra.The J = 1 ← 0 transitions of ¹²CH₃F in the v₂ = 1, v₃ = 1, v₅ = 1, and v₆ = 1 states and of ¹³CH₃F in the v₃ = 1 and v₆ = 1 states were observed, as well as the direct l-doubling transitions of ¹²CH₃F in the v₅ = 1 state. A preliminary analysis was carried out on the strong Coriolis interaction between the v₂ = 1 and v₅ = 1 states.     

The microwave spectrum of BrF5 in excited vibrational states: Coriolis interaction and an A1-A2 splitting of |akℓ|a ≠ 1 levels

The results of a numerical diagonalization treatment of the ν₅(B₁)-ν₉(E) Coriolis resonance in BrF₅ are presented. It is shown that the resonance is responsible for an A₁-A₂ splitting of the k? = ?3 lines in the v₉ = 1 state spectrum and of the |ak|a = 2 lines in the v₅ = 1 state spectrum. Assuming the sign of the constant R₆ is correctly known for BrF₅, the analysis of the Coriolis resonance provides the magnitudes and the signs of both the l-doubling constants q⁺ and $\text{q}{}^{\mathrm{?1}}$.     

多参考组态相互作用方法研究MgCl分子低激发态的光谱和分子常数

利用Davidson修正的内收缩多参考组态相互作用(ic-MRCI+Q)方法,结合相关一致全电子基aug-cc-pwCV5Z优化计算了MgCl分子5个低激发束缚电子态(5Λ–S)的势能曲线.为了得到高精度的光谱参量,计算中引入核价电子相关和相对论效应修正.基于修正的Λ-S束缚态的势能曲线,利用LEVEL8.0程序拟合得到相应的光谱常数、振动能级和分子常数,结果与其它的理论计算相比,本文的数值更接近实验值.这些结果说明高精度的计算方法和引入相关修正对分析光谱性质是非常必要的,这为进一步研究MgCl分子高激发态的光谱和跃迁特性提供理论支持.     

HOD分子在?1B1态的光解动力学： 产物OH/OD的分支比以及OD键解离能

利用H(D)原子里德堡态时间飞渡谱技术研究了HOD超声射流分子束在124 nm附近的?态光解动力学．实验测量了HOD分子在?态的转动分辨的吸收谱,并得到了五个转动峰下H+OD以及D+OH通道的产物总的平动能谱．通过对产物平动能谱的分析,得到了?态解离产物OH和OD的分支比,并与Β态和?态相应解离产物的分支比做了对比．实验结果确定了HOD分子OD键的解离能为41751.3±5 cm^-1.     

Microwave spectrum of methyl chloride in the excited vibrational states: Coriolis interaction between the ν2 and ν5 states

The rotational spectra of CD₃³⁵Cl, CD₃³⁷Cl, CH₃³⁶Cl, and CH₃³⁷Cl in the ν₂, ν₃, ν₅, and ν₆ states were observed and analyzed. A few lines of the J = 3 → 2 transition were also detected for ¹²CD₃³⁵Cl in the 2ν₃ state and for ¹³CD₃³⁵Cl in the ν₃ state. For CH₃³⁵Cl in the ν₆ state the present data on the J = 1 ← 0 and J = 2 ← 1 transitions were combined with the millimeterwave spectra reported by Sullivan and Frenkel to determine the molecular constants. Special attention was given to the ν₂ and ν₅ spectra which showed the effect of Coriolis resonance. By transferring some of the constants involved from the laser-Stark spectra we determined B₅^*, B₂^*, and q₅^* for CD₃Cl. The large effective q₅ constant permitted observation of the direct l-doubling transitions of high J. The analysis of the CH₃Cl spectra was much less complete than that on CD₃Cl because of limited data. The B rotational constants obtained were compared with the previous microwave and infrared results when available.By using the infrared data on ν₁ and ν₄ we evaluated the equilibrium B_e constants (α₄^B of CD₃³⁷Cl was estimated), and refined the equilibrium structure of methyl chloride reported by Duncan.     

Account of the fine structure of hydrogen atom levels in the effective emission cross sections of Balmer lines excited by electron impact in gases and plasma

The possibility of a correct account of the fine structure was shown for two limiting cases observed in beam and plasma experiments. A significant difference was found in the emission cross sections and the rate coefficients of direct and dissociative excitation of the H _α and H _β lines by electron impact in two limiting cases (e.g., this difference reaches an order of magnitude for dissociative excitation of the H _β line). The most reliable data on the cross sections and the rate coefficients of direct and dissociative excitation of the H _α and H _β lines by electron impact were found for both limiting cases. It was shown that, among the first four lines of Balmer series (rather easily detected), only the first two lines, i.e., H _α and H _β, can be currently employed in plasma spectroscopy studies because of the absence of data on the partial excitation cross sections of hydrogen atom nl-sublevels with n≥5.     

The microwave spectrum of sodium tetrahydroborate NaBH4 in excited vibrational states: Coriolis interaction between the Na-BH4 stretching and the BH4 rocking vibrations

Two sets of vibrational satellites have been observed in the rotational spectrum of sodium tetrahydroborate NaBH₄, and have been assigned to the non-degenerate, Na—BH₄ stretching and the degenerate BH₄ rocking (or internal rotation) states. The observation was extended from the J = 11 ← 10 up to J = 20 ← 19 transitions. The vibrational satellites showed anomalous K structure; higher-K lines of the non-degenerate state appeared at higher frequencies, in reverse to those of the ground state, whereas the spectra in the degenerate state exhibited a K pattern similar to but somewhat more widely spread than that of the ground state. These anomalies are ascribed to the Coriolis interaction between the two excited vibrational states. The spectra observed were analysed using a C_3v symmetric-top rotational Hamiltonian, which took into account the Coriolis interaction explicitly. The A rotational constants, the energy difference δE between the two interacting vibrational states, and the first- and second-order Coriolis interaction constants have been derived.     

Mössbauer studies of dilute Au:Er alloys: Obervation of hyperfine structure of ground and excited CEF levels

The hyperfine structure of dilute ¹⁶⁶Er impurities in Au has been investigated between 1.8 and 60 K by Mössbauer spectroscopy. The hyperfine spectrum of the Γ₇ electronic ground state is clearly observed below 4.2 K while at higher temperatures there is an indication of the contribution from the excited CEF-states Γ⁽¹⁾₈ and Γ₆. Using Hirst's relaxation theory for the Γ₇ ground state the magnetic hyperfine coupling constant A=(247±3) MHz and the exchange coupling constant J_sf=(0.10±0.02)eV were derived. A quadruple coupling constant B of about 1 MHz was estimated from the hyperfine pattern of the Γ⁽¹⁾₈ quartet.     

Local hydrated structure of an Fe2+/Fe3+ aqueous solution: an investigation using a combination of molecular dynamics and X-ray absorption fine structure methods

The hydrated shell of both Fe2+ and Fe3+ aqueous solutions are investigated by using the molecular dynamics (MD) and X-ray absorption structure (XAS) methods. The MD simulations show that the first hydrated shells of both Fe2+ and Fe3+ are characterized by a regular octahedron with an Fe-O distance of 2.08 for Fe2+ and 1.96 for Fe3+, and rule out the occurrence of a Jahn-Teller distortion in the hydrated shell of an Fe2+ aqueous solution. The corresponding X-ray absorption near edge fine structure (XANES) calculation successfully reproduces all features in the XANES spectra in Fe2+ and Fe3+ aqueous solution. A feature that is located at energy 1 eV higher than the white line (WL) in an Fe3+ aqueous solution may be assigned to the contribution of the charge transfer.     

Microwave spectrum of silicon difluoride in the excited vibrational states,equilibrium structure,anharmonic potential function,and ν1-ν3 Coriolis resonance

The microwave spectrum of SiF₂ was identified in the excited states of the stretching vibrations. It was found that the Coriolis resonance between the v₁ = 1 and v₃ = 1 vibrational states has perturbed very much the spectra of these states. An extensive analysis of the Coriolis resonance gave a very accurate value of the difference between the ν₁ and ν₃ fundamental frequencies, ν₁ - ν₃ = ? 15.395 ± 0.001 cm^?1 and, thus, gave a strong basis to the assignment of the stretching modes by Khanna et al. An intervibrational-state transition, v₁ = 1, 8₅₄ ← v₃ = 1, 8₁₇ was identified.The observed rotational constants in the v₁ = 1 and v₃ = 1 states were combined with those in the ground and v₂ = 1 states by Rao and Curl to obtain the equilibrium structure, harmonic force constants and complete sets of the cubic and the third-order potential constants.     

Investigation of flame structure and burning behaviour in an IC engine simulator by 2D-LIF of OH radicals

Turbulent combustion of propane/air mixtures in an internal combustion engine simulator has been studied by 2D-LIF of OH radicals formed in the combustion process. A laser light sheet of thickness 75 m at 308 nm was used for excitation of OH and the fluorescence imaged onto an image-intensified CCD-camera. From the large number of images recorded, information on the burning behaviour of various flame structures could be obtained. In particular, flame extinction was clearly observed for lean (=1.5) mixtures.     

Stereoelectronic properties of photosynthetic and related systems: Ab initio configuration interaction calculations on the ground and lower excited singlet and triplet states of magnesium chlorin and chlorin

Ab initio configuration interaction wavefunctions and energies are reported for the ground state and many low-lying singlet and triplet states of magnesium chlorin and chlorin, and are employed in an analysis of the electronic absorption spectra of these systems.In chlorin, the calculated visible spectrum consists of two ${}^1\text{(π, π}{}^1\text{)}$ states, the lower energy, y-polarized state exhibiting moderate absorption intensity in contrast to the very weak absorption of the higher energy x-polarized state. The configurational composition of both states is well described by the four-orbital model. Five ${}^1\text{(π, π}{}^1\text{)}$ states are responsible for the Soret band envelope. A moderately intense y-state lies under the low energy edge of the band envelope, while two x-polarized states of moderate and strong intensity, respectively, are responsible for the band maximum. The final two ${}^1\text{(π, π}{}^1\text{)}$ states lie at the high energy edge of the Soret band and introduce a measure of asymmetry into the band envelope. Two ${}^1\text{(n, π}{}^1\text{)}$ states of very weak oscillator strength are also found in this region of the spectrum. All the Soret states are of complex configurational composition, and several of the higher lying states contain contributions from doubly excited configurations.The calculated visible spectrum of magnesium chlorin also consists of two ${}^1\text{(π, π}{}^1\text{)}$ states, with the weakly absorbing x-polarized state lying approximately 200 cm^?1 lower in energy than the moderately intense y-polarized state. The configurational composition of both states is well described by the four-orbital model. Four ${}^1\text{(π, π}{}^1\text{)}$ states constitute the bulk of the intensity in the Soret band envelope. In distinction to chlorin, the moderately intense ${}^1\text{(π, π}{}^1\text{)}$ state at the low energy edge of the band envelope is x-polarized. Two intense ${}^1\text{(π, π}{}^1\text{)}$ states of y- and x-polarization, respectively, constitute the band maximum region, and a single x-polarized state of moderately strong intensity can be assigned to the high energy shoulder of the band envelope. Two other weakly absorbing ${}^1\text{(π, π}{}^1\text{)}$ states are also found in this region, along with another weakly absorbing state of mixed in-plane and out-of-plane polarization. No clearly defined ${}^1\text{(n, π}{}^1\text{)}$ states are observed. As was the case for chlorin, all the Soret states are of complex configurational composition, and some of the higher energy states contain significant contributions from doubly excited configurations.Chlorin and magnesium chlorin both possess three ${}^3\text{(π, π}{}^1\text{)}$ states which lie below S₁ and a single ${}^3\text{(π, π}{}^1\text{)}$ which lies slightly above S₂. All four of the low-lying ${}^3\text{(π, π}{}^1\text{)}$ states in each molecule are well described by the four-orbital model, with T₁ being essentially a single configuration in each case. The remainder of the ${}^3\text{(π, π}{}^1\text{)}$ states are clustered in the same energetic region as the comparable ${}^1\text{(π, π}{}^1\text{)}$ Soret states, with comparably complex configurational compositions.Dipole moments and charge distributions for low-lying singlet and triplet states are also reported, and are used to rationalize chemical reactivity characteristics.     

The interaction between first excited state hydrogen atoms and a different non-degenerate atom: an example of second-order resonance forces

The interaction of a first excited state hydrogen atom with a different non-degenerate atom is considered in the R ^-1 multiple approximation. The interaction energies for the Π states arising from this interaction have the form usually associated with second-order dispersion energies while those for the Σ states behave quite differently as a function of R. Because of a second-order ‘resonance within one molecule effect’ the second-order Σ-state energies do not possess single R ^-1 expansions that are formally valid for all values of R consistent with the multipole treatment. The expansions of these Σ-state energies, that are valid for ‘small’ R, contain terms varying as both even and odd powers of R ^-1; the lead R ^-7 ‘odd’ term competes strongly with the usual R ^-6 dispersion energy. The expansions that are valid for ‘large’ R contain terms varying as even powers of R ^-1 only and usually have little physical meaning. The He(¹S)-H(n=2) interaction is considered as a specific example of these results and the interaction energies for this system are evaluated through O(R ^-8) by using one-centre pseudostate methods. The general significance of the results is also discussed briefly.     

Resonant Raman Scattering of synchrotron X-rays by neodymium: Observation of fine structure in K-L-RRS and of K-N-RRS

Using monochromatized synchrotron radiation with variable photon energyE _i =43.01...43.35 keV, Resonant Raman Scattering (RRS) by Neodymium atoms (K-shell binding energyB _1s=43.57 keV) was investigated. For the first time the fine structure splitting in a K-L-RRS spectrum due to the energy difference of the L₂ and L₃ subshells was observed. In addition, the first observation of K-N-RRS in the spectrum of scattered photons is reported. The measured double-differential RRS cross sections are, on an absolute scale, in very good agreement with those calculated in the non-relativistic dipole approximation, modified by relativistic corrections.     

Si2O2 molecule: structure of ground state and the excited properties under different external electric fields

Geometry and vibrational frequencies of the ground state of Si 2 O 2 molecule are studied using density function theory (DFT) at the level of cc-pvtz and 6-311++G.It is found that the optimizing value by B3lyp/cc-pvtz is closer to the experimental data.The excited properties under different external electric fields are also investigated by the time-dependent-DFT method.Transitions from the ground state of Si 2 O 2 molecule to the first singlet state under different external electric fields can take place more easily.The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.     

Energy levels,luminescence and electronic structure of ZnS:Tm3+

Energy levels, densities of states, electronic densities, electrostatic interaction integral parameters F_k and spin-orbit coupling parameters ζ_4f for ZnS: Tm³⁺ are calculated self-consistently, using both one-electron local density discrete variational non-relativistic Hartree-Fock-Slater (HFS) and relativistic Dirac-Slater (DS) cluster models. In these calculations, both spin-restricted and spin-polarized models are considered. The finite clusters calculated include TmS₄ and TmS₄Zn₁₂ clusters for cubic ZnS, which are embedded in the crystal environment. The spin-orbit coupling parameter ζ_4f derived from DS cluster calculations is equal to 2689 cm^-1, rather near the result of the relativistic Hartree-Fock free ion model. The parameters F_k and ζ_4f are further calculated from the 4f radial wave function obtained by solving the HFS and the DS atomic equations. It is shown that by decreasing the effective exchange-correlation potential, these parameters can be reduced to approximately match empirical values. A comparison of the excited energy level scheme of ZnS:Tm derived from the calculated parameters and the experimental spectra is presented.