Collisional — Radiative Model of Helium Plasma. II. Global Population Coefficients

We present results of our calculation of global population coefficients based on a collisional — radiative model of the helium plasma. The results are given for 2³P, 2¹P, 3³S, 3¹S, 3³P, 3¹D, 3³D, 3¹P, 4³ and 4¹ states of helium atoms. We consider electron densities from 10⁷ to 10¹⁸ cm^?3 and electron temperature from 1 to 10 eV. The electron distribution function is considered to be Maxwellian and the plasma to be radiatively thin.     

Electronic pair excitations of Mn2+ and Ni2+ in perovskite fluorides: involvement of the 3 T 1g a state of Ni2+

Crystals of KZnF₃ and KMgF₃ doped with Mn²⁺ and Ni²⁺ were used to study the spectroscopic properties of Mn²⁺-F^--Ni²⁺ pairs. Pair transitions to the doubly excited states ⁴ E_g ^a , ⁴ A _1g (Mn)³ T _1g ^a (Ni) and ⁴ E_g ^b (Mn)³ T _1g ^a (Ni) were observed. The participation of the spin-allowed ³ A _2g →³ T _1g ^a excitation on Ni²⁺ in the pair transition is explained by spin-orbit mixing between ³ T _1g ^a and ¹ E_g . The prominent electronic origins are assigned to the double spin-flip transitions ⁶ A _1g (Mn)³ A _2g (Ni) →⁴ E_gu(Mn)³ T _1g ^a (Γ₃)v(Ni) and ⁴ A _1g (Mn)³ T _1g ^a (Γ₃)v(Ni). The former lie at lower energy and are more intense than the corresponding ⁶ A _1g (Mn)³ A _2g (Ni) →⁴ E_gv(Mn)³ T _1g ^a (Γ₃)u(Ni) transitions involving two orbital jumps. The well-resolved vibronic structure is composed of three basic vibrations of ～ 150 cm^-1, ～ 294 cm^-1 and ～ 508 cm^-1 in the KZnF₃ host.     

Determination of hyperfine structures and Rydberg convergence limits of selected optical transitions in 93Nb using resonance ionization spectroscopy

Several two- and three-step schemes for resonance ionization of ⁹³Nb with field ionization of Rydberg levels were investigated in the context of feasibility studies of using ^93m Nb/⁹³Nb isomer ratio determination for fast neutron dosimetry. Hyperfine structures of the states 4d ⁴(a ⁵ D)5p ⁴ D ₁ ^2/0 , 4d ³5_s(a ⁵ P)5P ⁶ D ₁ ^2/0 , 4d ³5s(a ⁵ F)5p ⁶ F ₁ ^2/0 , and 4d ³5s(a ⁵ F)6s ⁶ F _1/2 of ⁹³Nb were measured. The Rydberg spectra of the excitation schemes were measured and corresponding ionization limits estimated.     

Energy Levels of the Single Excited States in the Boron Isoelectronic Sequences

Energy levels of the single excited 1s²2s²ns (²S), 1s²2s²np (²P), 1s²2s²nd (²D) and 1s²2s²nf (²F), n = 3-8 states for the boron isoelectronic sequence are calculated using the simple configuration Hartree-Fock method. Good agreement is obtained between our results and previous experimental and theoretical data.     

Photoionization of Al IV (neon-type) from its ground 2s 22p 6 1 S e and excited 2s 22p 53p 3,1 P 0 3 S e states using the R-matrix method

The R-matrix method is used to calculate the total photoionization cross-sections from the ground 2s ²2p ^{6 1} S ^e and the first three excited 2s ²2p ⁵3p ^3,1 S ^e states of Al IV, for photon energies ranging from the first ionization threshold to just above the second threshold of the residual ion Al V. The two lowest LS terms of Al V − 2s ²2p ^{5 2} P ⁰, 2s2p ^{6 2} S ^e, 2s2p ^{6 2} S ^e, represented by sophisticated configuration interaction wavefunctions, are included in the R-matrix calculation. The resulting cross-sections are affected by Rydberg series of resonances converging to the 2s2p ^{6 2} S ^e excited threshold.     

Connection Considerations of Gravitational Field in Finsler Spaces

Some alternative connection structures of the Finslerian gravitational field are considered by modifying the independent variables (x,y) (x: point and y: vector) in various ways. For example, (x ^k ,y ⁱ ) (k,i = 1,2,3,4) are changed to (x ^k ,y ⁰) (y ⁰: scalar) or (x ⁰,y ⁱ ) (x ⁰: time axis); (x ^k ,y ⁱ ) are generalized to (x ^k ,y ⁱ ,p _i ) (p _i : covector dual to y ⁱ ) or (x ^k ,y ⁱ ,q _a ) (q _a : covector different from p _i ); (x ^k ,y ⁱ ) are further generalized to (x ^k ,y ^(a)i ) (a = 1,2,…,m), (y ^(a): (a)th vector), etc.     

基于火焰发射光谱的转动温度和振动温度的测量

利用光学多通道分析仪(OMA)对酒精和煤油在大气中燃烧时的火焰发射光谱进行了分析.实验发现上述火焰发射光谱在275-600 nm波段范围内存在多支辐射强度很大的带状分子光谱,其中以OH自由基A²Σ⁺→X²Π_r(300-330 nm),CH自由基A²Δ→X²Π(410-440 nm)和C₂自由基A³Π_g→X³Π_u(500-520 nm)电子带系的发射光谱最为强烈.实验中采用高分辨率光栅对OH自由基A²Σ⁺→X²Π_r和CH自由基A²Δ→X²Π电子带系发射光谱的精细结构进行了分析.与此同时,本文基于分子光谱理论计算了不同转动温度和振动温度条件下OH自由基A²Σ⁺→X²Π_r和CH自由基A²Δ→X²Π电子带系发射光谱的强度分布,同时通过理论计算光谱和实验光谱进行比较确定了酒精燃烧火焰的转动温度和振动温度. 关键词： 火焰发射光谱 谱线强度 转动温度 振动温度     

The strong coupling constants of excited positive parity heavy mesons in light-cone QCD

We calculate the strong coupling constants g_p^**p^*π, where P^** (D^**, B^**) is the 1⁺ p-wave state, in the framework of the light-cone QCD sum rules, and using these values ofg_p^**p^*π , we compute the hadronic decay widths forD^** → D^* π and B^** → B^* π.     

Two-electron excitation in helium-like ions by electron impact

Calculation of cross-sections for the two-electron excitation in helium-like ions by electron impact employing Coulomb-Born-Oppenheimer (CBO) approximation is presented. Analytical expressions for the differential and total scattering cross-sections without using partial wave expansion of the wavefunction reported earlier have been used. The total and differential scattering cross-sections for each of the excitations 1s ^{2 1} S* → 2s ^{2 1} S ^e , 2s2p ^1.3 P ⁰, 2p ^{2 1} S ^e ,³ P ^e,¹ D ^e in Be²⁺ and B³⁺ are computed. Results for Li⁺ reported earlier are also included for comparison.     

Nuclear magnetic double resonance studies of the effect of deuterium substitution upon 1 J(31P-H) in dimethyl phosphite

A study of the absorption of light by pairs of exchange coupled manganese ions in the perovskite fluorides KMgF₃ and KZnF₃ has been made using the technique of high resolution phosphorescence excitation spectroscopy. Transitions to the following pair states have been observed: ⁶ A _1g ⁴ T _1g ^a ; ⁶ A _1g ⁴ E _g ^a ; ⁶ A _1g ⁴ A _1g ; ⁶ A _1g ⁴ E _g ^b ; ⁴ T _1g ^{a 4} T _1g ^a ; ⁴ E _g ^{a 4} T _1g ^a and ⁴ A _1g ⁴ T _1g ^a . Quantitative estimates of intensities have been made for some of these transitions as well as estimates of the effective exchange parameters. A detailed analysis of the transition ⁶ A _1g ⁶ A _1g → ⁶ A _1g ⁴ A _1g provides confirmation of the Tanabe mechanism of exchange induced absorption of light by pairs of transition metal ions. It is shown that absence of MCD in this pair absorption is predicted by the Tanabe mechanism.     

Die EINSTEIN-Gruppe und die Symmetrie-Gruppen der Gravitationstheorie

The transformations x^?α = x^?α(x^β, g_μn?) in the function space of the g_μn?(x^λ) are corresponding to the coordinate transformations x^α = x^α(x^β) with some non-covariant conditions on the g_μn?(x^λ). Therefore, the transformations in the function space are corresponding to subgroups of the EINSTEIN group. The conditions for the g_μn? may be given in the space- time V₄ or on submanifolds (points, curves, surfaces and hypersurfaces) of the V₄. – A special case of the last problem is given by the CAUCHY conditions or by the DIRAC constraints for a special choice of the coordinates on a CAUCHY hypersurface x⁰ = 0. Then, the transformations x^?α = x^?α(x^l, g_rs, p^mn) in the phase space are EINSTEIN transformations preserving the synchronicity for x⁰ → 0.     

CrHn(n=0,+1,+2)分子及离子的势能函数

用原子分子反应静力学原理推导出CrHⁿ(n=0，+1，+2)的电子状态及其离解极限. 对H原子采用6-311++G^**基组，对Cr原子采用SVP(split valence polarization)全电子基组，用B3PW91方法计算了它们的平衡几何、电子状态，在此基础上分别计算CrH，CrH⁺的Murrell-Sorbie解析势能函数和CrH²⁺的解析势能函数及其对应的力常数、光谱参数，理论计算值与实验值和文献计算值符合较好. 从离解极限和通道解释了不同的势能函数形状. 计算表明：CrH⁺的势能曲线均具有对应于稳定平衡结构的极小点，说明CrH⁺可稳定存在. 而CrH²⁺离子的势能曲线对应于不稳定的排斥态，说明CrH²⁺是不稳定的. 关键词： n(n=0')" href="#">CrHⁿ(n=0 +2) 势能函数 光谱参数 稳定性     

Dielectric spectroscopy characteristics of ferroelectric Pb0.77K0.26Li0.2Ti0.25Nb1.8O6 ceramics

Temperature and frequency dependence of dielectric constant and conductivity properties of Pb_0.77K_0.26Li_0.2Ti_0.25Nb_1.8O₆ (PKLTN) ceramics are modelled through the universal dielectric response (UDR). Partial substitution of Ti⁴⁺ for Nb⁵⁺ was compensated by charge and the creation of oxygen vacancies according to the Kroger-Vink notation. The electrons released by this reaction are captured by Nb⁵⁺ and Ti⁴⁺ to generate Nb³⁺ and/or Ti³⁺. The hopping of electrons between Nb⁵⁺–Nb³⁺ and Ti⁴⁺–Ti³⁺ are believed to participate in conductivity. Characterization of the dielectric constant has been performed from room temperature to 590°C in the frequency range from 45 Hz to 5 MHz. The measured dielectric constant obeyed Jonscher's dielectric dispersion relations: ε ^l = ε _∞ + sin(n(T)π/2)(a(T)/ε ₀)(ω^{n ( T )?1}) and ε ^ll = σ/iε ₀ ω + cos(n(T)π/2)(a(T)/ε ₀)(ω^{n ( T )?1}). Cole-Cole plots inclined at an angle (1 ? n(T))π/2 and followed the trend of universal material behavior ε _∞ + A(T)(ω^{n ( T )?1}). The exponent n(T) and coefficient A(T) = (a(T)S/L) exhibited a minimum and maximum at T _c = 425°C, respectively. The conductivity studies show the contribution of the hopping of bound charge carriers to conduction in PKLTN.     

Computational study of collisional energy transfer and quasi-continuous population inversions in laser-pumped Ca vapor

A computational study of population inversion between several pairs of excited states viz 3d4p ³ F-4s3d ³ D, 4s5s ³ S-4s4p ³ P and 4s3d ³ D-4s4p ³ P in Ca vapor pumped on the 4s ^{2 1} S ₀-4s4p ³ P ₁ transition is presented. The main aim is to investigate the influence of various atomic processes in creating and sustaining the population inversion for long times after the excitation pulse. The delicate interplay between superelastic energy transfer to free electrons, energy pooling collisions and cascaded recombination is particulary examined. It is noted that quasi-continuous population inversion can be readily excited on the 4s3d ³ D-4s4p ³ P transitions; and under some conditions, also on the 4s5s ³ S-4s4p ³ P transitions. Furthermore, inversion on the 3d4p ³ F-4s3d ³ D transitions can also be excited for a considerable length of time. The results may be useful in designing and developing quasi-cw metal vapor lasers.     

Group theoretical aspects ofU B(6) ⊗U F(20) symmetry limits of IBFM related to theU B(5) andO B(6) limits of IBM

TheU ^B(6)⊗U ^F(20) Bose-Fermi dynamical symmetry of interacting boson-fermion model arises when the odd nucleon occupies single particle orbits withj=1/2, 3/2, 5/2, and 7/2. The subgroup structures ofU ^B(6)⊗U ^F(20) related to theU ^B(5) andO ^B(6) limits of sdIBM (U ^B(6)) are analysed. Broadly speaking,U ^B(6)⊗U ^F(20) admitsU ^BF(5)⊗U _s ^F (4), Spin^BF(5)⊗U _k ^F (5) andU ^BF(5)⊗U _s ^F (2) limits withU ^B(5) core and Spin^BF(6),O ^BF(5)⊗U _s ^F (4), Spin^BF(6)⊗U _k ^F (5) andO ^BF(6)⊗U _s ^F (2) limits withO ^B(6) core respectively. For each of these seven symmetry limits, group chains, quantum numbers labelling the basis states, generators and Casimir operators for the various subgroups and energy formulas are given. Recoupling coefficients (reduced Wigner coefficients) for constructing wavefunctions of low-lying states are tabulated and these will allow (together with sdIBMU ^B(5) andO ^B(6) limit results) one to calculateB(E2)’s,B(M1)’s, one and two nucleon transfer strengths etc. in the seven symmetry limits. Experimental examples for theU ^B(6)⊗U ^F(20) symmetry limits are briefly discussed.     

Dispersion and polarization interactions of the strontium atom

Dispersion coefficients involving the 5s ^{2 1} S ^e and 5s5p ^1,3P ^o states of strontium are determined from a large basis configuration interaction calculation. Dispersion coefficients are presented for the strontium dimer and also for strontium interactions with hydrogen and the rare gases. Polarizabilities and oscillator strengths from some low lying states are also given. The ground state polarizability and that of the 5s5p ¹P ^o and 5s4d ¹D ^e states are very similar in size.     

Precision measurements of optical excitation functions for zinc atom

The excitation of zinc atoms by ultramonoenergetic electrons is experimentally studied. The optical excitation functions for 19 atomic spectral lines that originate from the n ¹ S ₀, 4¹ P ₁, n ¹ D ₂, n ³ S ₁, 4³ P ₁, 6³ P ₂, and n ³ D _j levels are studied in detail. In the excitation functions measured from the excitation threshold to 19 eV for the spectral lines originating from the n ¹ S ₀, n ³ S ₁, n ¹ D ², and n ³ D _j levels, specific features caused by postcollision interactions of emitted and scattered electrons are observed for the first time in the energy region of 10.9–17.0 eV near the thresholds of autoionization states.     

The high-resolution infrared spectrum of ethylene in the 1800–2350 cm−1 spectral region

Fourier transform spectra of ethylene (C₂H₄) have been recorded in the 1800–2350?cm^?1 (4.3–5.6?µm) spectral region using a Bruker IFS125HR spectrometer at a resolution of 0.004?cm^?1 leading to the observation of six vibrational bands, ν ₇?+?ν ₈, ν ₄?+?ν ₈, ν ₆?+?ν ₁₀, ν ₆?+?ν ₇, ν ₄?+?ν ₆ and ν ₃?+?ν ₁₀. The corresponding upper state ro-vibrational levels were fit using a Hamiltonian matrix accounting for numerous interactions. A satisfactory fit could be obtained using a polyad of nine interacting states {8¹10¹,?7¹8¹,?4¹8¹,?8¹12¹,?6¹10¹,?6¹7¹,?4¹6¹,?3¹10¹,?3¹7¹} of which three (8¹10¹, 8¹12¹ and 3¹7¹) are unobserved dark states. As a result a much more accurate and extended set of Hamiltonian constants were obtained than previously derived. The following band centers were determined: ν ₀(ν ₇?+?ν ₈)?=?1888.9783(20)?cm^?1, ν ₀(ν ₄?+?ν ₈)?=?1958.2850(20)?cm^?1, ν ₀(ν ₆?+?ν ₁₀)?=?2047.7589(20)?cm^?1, ν ₀(ν ₆?+?ν ₇)?=?2178.011(60)?cm^?1, ν ₀(ν ₄?+?ν ₆)?=?2252.8026(24)?cm^?1 and ν ₀(ν ₃?+?ν ₁₀)?=?2171.2397(20)?cm^?1. Finally, a synthetic spectrum that could be useful for ethylene detection in planetary atmospheres was generated.     

Impact broadening and shift rates for the 6p2 3PJ′ → 7s 3P J o transitions of lead induced by collisions with argon and helium

The collisional broadening and shift rate coefficients of the 283.39 nm (6p ^{2 3}P₀ → 7s ³P₁ ^o ), 364.06 nm (6p ^{2 3}P₁ → 7s ³P₁ ^o ), 368.45 nm (6p ^{2 3}P₁ → 7s ³P₀ ^o ) and 405.90 nm (6p ^{2 3}P₂ → 7s ³P₁ ^o ) Pb lines by He and Ar have been measured by fitting the experimental absorption line shapes to theoretical Voigt profiles. The absorption measurements were performed in a resistively heated, Pb loaded oven with an integrated dc noble gas discharge to produce also Pb atoms in the 6p ^{2 3}P¹ and 6p ^{2 3}P² metastable states. The diffusion of the metastable atoms out of the discharge zone into the neutral noble-gas atmosphere enabled the line-shape and shift measurement of the lines involving the metastable states without the influence of the discharge plasma.