State-specific rotational energy transfer in OH (A 2Σ+, v′=0) by some combustion-relevant collision partners

State-to-state rotational energy transfer (RET) co-efficients were determined for inelastic collisions of OH (A ²⁺, v=0) with N₂, CO₂, and H₂O at 300 K. The experimental procedure described previously allows the direct evaluation of state-specific RET coefficients from time-resolved laser-induced fluorescence (LIF) measurements without any assumptions on the RET. The results show strikingly different RET behaviour for the three collision partners. The data can serve as a basis for a comparison with dynamic collision models.A. Jörg is now with IBM Corporation, Frankfurt, Fed. Rep. Germany     

A theoretical study of energy transfer in the quenching of O(1 D 2) by CO(1Σ+)

Energy transfer processes occurring during the collisional quenching of O(¹ D) by CO(¹Σ⁺) are studied using a classical collision complex model together with potentials previously derived for the C(³ P) + O₂(³Σ _g ^-) reaction. Room temperature quenching rate constants, electronic-vibrational transfer efficiencies and product vibrational state distributions are in good agreement with experiment. The calculated and experimental temperature dependences of the electronic-vibrational transfer efficiencies and vibrational populations, however, disagree. The effect of using vibrationally excited CO as a quenching partner is studied and shown to result in a lowering of the quenching rate constant by a factor of 4 at room temperature. Enhancement of initial translational energy by the equivalent of a vibrational quantum of energy leads to an even larger decrease in the rate constant. This difference between vibrational and translational energy enhancement is interpreted in terms of an increased centrifugal barrier in the latter case.     

Measurements of rotational energy transfer and quenching in OHA 2 σ +,υ′ = 0 at elevated temperature

Total rotational energy transfer rates have been measured at 1330 K for specific rotational levels in the OHA ^{2 +}, = 0 state in collisions with H₂O. Rotational levels ranging fromN = 0 to 15 were studied. Measurements were performed in the post-flame region of a stoichiometric H₂/O₂/He flame operating at 25 mbar. Quenching rates following excitation of individual upper rotational states were also measured. The RET and quenching rates both exhibit monotonic decreases with increasing rotational quantum number.     

Four-wave mixing in CO via the C 1Σ+ (υ′=0) state

Coherent vacuum ultraviolet (VUV) radiation was generated by four-wave difference frequency mixing (_VUV=2₁–₂) of pulsed dye laser radiation in carbon monoxide (CO). The frequency ₁ was tuned to the C ¹⁺(=0)X ¹⁺(=0) two-photon transition, while the dye laser frequency ₂ was scaned around 17650 cm^–1 which corresponds to the A ¹(=7)«C ¹⁺(=0) transition energy. The VUV intensity was found to be strongly wavelength dependent. The analysis of the spectrum revealed (i) that the VUV intensity was enhanced by the rotational levels of the A ¹(=7) state and (ii) that the off-resonance excitation in the C ¹⁺(=0)X ¹⁺(=0) two-photon transition greatly contributed to the present four-wave mixing process. The effects of pumping laser detuning, saturation and foreign gases are briefly discussed.     

State-to-state dynamics of F(~2P) + HO(~2Π) → O(~3P) + HF(~1Σ~+)reaction on 1~3A〞 potential energy surface

State-to-state time-dependent quantum dynamics calculations are carried out to study F(~2P) + HO(~2Π) → O(~3P) +HF(~1Σ~+) reaction on 1~3A〞 ground potential energy surface(PES). The vibrationally resolved reaction probabilities and the total integral cross section agree well with the previous results. Due to the heavy–light–heavy(HLH) system and the large exoergicity, the obvious vibrational inversion is found in a state-resolved integral cross section. The total differential cross section is found to be forward–backward scattering biased with strong oscillations at energy lower than a threshold of 0.10 eV, which is the indication of the indirect complex-forming mechanism. When the collision energy increases to greater than 0.10 eV, the angular distribution of the product becomes a strong forward scattering, and almost all the products are distributed at θ_t = 0°. This forward-peaked distribution can be attributed to the larger J partial waves and the property of the F atom itself, which make this reaction a direct abstraction process. The state-resolved differential cross sections are basically forward-backward symmetric for v' = 0, 1, and 2 at a collision energy of 0.07 eV; for a collision energy of 0.30 eV,it changes from backward/sideward scattering to forward peaked as v increasing from 0 to 3. These results indicate that the contribution of differential cross sections with more highly vibrational excited states to the total differential cross sections is principal, which further verifies the vibrational inversion in the products.     

The pure rotational spectrum of ZnS (XΣ)

The pure rotational spectrum of ZnS (X¹Σ⁺) has been measured using direct-absorption millimeter/sub-millimeter techniques in the frequency range 372-471 GHz. This study is the first spectroscopic investigation of this molecule. Spectra originating in four zinc isotopologues (⁶⁴ZnS, ⁶⁶ZnS, ⁶⁸ZnS, and ⁶⁷ZnS) were recorded in natural abundance in the ground vibrational state, and data from the v = 1 state were also measured for the two most abundant zinc species. Spectroscopic constants have been subsequently determined, and equilibrium parameters have been estimated. The equilibrium bond length was calculated to be r_e ∼ 2.0464 Å, which agrees well with theoretical predictions. In contrast, the dissociation energy of D_E ∼ 3.12 eV calculated for ZnS, assuming a Morse potential, was significantly higher than past experimental and theoretical estimates, suggesting diabatic interaction with other potentials that lower the effective dissociation energy. Although ZnS is isovalent with ZnO, there appear to be subtle differences in bonding between the two species, as suggested by their respective force constants and bond length trends in the 3d series.     

MgH分子X2Σ+,A2Π和B2Σ+电子态的势能函数

利用QCISD(T),SAC-CI方法和cc-pVQZ,aug-cc-pVTZ,6-311 G及6-311 G(3df,2pd)基组,对MgH分子的基态X2Σ ,第一简并激发态A2Π和第二激发态B2Σ 的结构进行优化计算.通过对4个基组计算结果进行比较,得出6-311 G(3df,2pd)基组为最优基组.使用6-311 G(3df,2pd)基组和QCISD(T)方法对基态X2Σ ,SAC-CI方法对激发态A2Π和B2Σ 进行单点能扫描计算,然后采用Murrell-Sorbie函数及修正的Murrell-Sorbie C6函数进行拟合,得到了相应电子态的势能函数参数和对应的光谱常数.计算结果表明,用修正的Murrell-Sorbie C6函数计算得到的MgH分子基态和第一简并激发态的光谱常数ωe,ωexe,Be,αe与实验数据吻合很好.表明修正后的Murrell-Sorbie C6函数能更为准确地描述MgH分子的基态和第一激发态的势能函数.     

AlF的X1Σ+,A1Π和B1Σ+态的势能函数

使用SAC/SAC-CI和D95 、6-311 g及D95(d)等基组,分别对AlF的基态X1Σ 、第一简并激发态A1Π和第二激发态B1Σ 的平衡结构和谐振频率进行了优化计算.对所有计算结果进行比较,得出D95(d)基组为最优基组;运用D95(d)基组和SAC方法对基态X1Σ ,SAC-CI方法对激发态A1Π和B1Σ 进行单点能扫描计算,并用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的势能函数解析式,由得到的势能函数计算了与X1Σ 、A1Π和B1Σ 态相对应的光谱常数,结果与实验数据较为一致.     

Near-resonant electronic energy transfer induced by first- and second-order long-range potentials between the two states A1Σu+ and X1Σg+ of Li2 and Na2

Collision-induced rotational transitions between different electronic states are treated theoretically in the Born approximation for a second-order long-range interaction potential. It is shown that the experimentally observed cross sections for resonant channels in the A → X transfer of Li₂ are reproduced by this simple calculation taking the two terms' first-order dipole-dipole and second-order interaction potentials into consideration.     

Vibrational and rotational excitation effects of the N(2D) + D2(X1Σg +) → ND(X3Σ+) + D(2S) reaction

The effects of the rovibrational excitation of reactants in the N(²D) + D₂(X¹Σ_g⁺) → ND(X³Σ⁺) + D(²S) reaction are calculated in a collision energy range from the threshold to 1.0 eV using the time-dependent wave packet approach and a second-order split operator. The reaction probability, integral cross-section, differential cross-section and rate constant of the title reaction are calculated. The integral cross-section and rate constant of the initial states v = 0, j = 0, 1, are in good agreement with experimental data available in the literature. The rotational excitation of the D₂ molecule has little effect on reaction probability, integral cross-section and the rate constant, but it increased the sideways and forward scattering signals. The vibrational excitation of the D₂ molecule reduced the threshold and broke up the forward–backward symmetry of the differential cross-section; it also increased the forward scattering signals. This may be because the vibrational excitation of the D₂ molecule reduced the lifetime of the intermediate complex.     

碰撞诱导振动能量转移K_2[1~1Σ_u~+(v′=2)]+He,H_2→K2[1~1Σ_u~+(v′=1,3)]+He,H_2

在样品池条件下,利用激光诱导荧光方法研究了K2[11Σ+u(v′=2)]+He,H2→K2[11Σ+u(v′=1,3)]+He,H2的碰撞能量转移。池温保持在420 K,He和H2气压在40~250 Pa之间变化。脉冲激光激发K2基态至11Σ+u(v′=2)态,荧光中含有直接和碰撞转移荧光成分,记录直接11Σ+u(v′=2)→11Σ+g(v″=0)荧光发射的时间分辨强度。在发射开始时v′=2能级的布居未受v′=1,3→v′=2碰撞转移的影响,因此光强为一纯指数曲线,从强度的对数值给出的直线斜率得到有效寿命,由Stern-Volmer方程得到v′=2→v″=0的辐射寿命为(36±7)ns,v′=2与He和H2碰撞的总的转移截面分别为(3.0±0.5)×10-16cm2和(6.4±1.2)×10-15cm2。在不同的He和H2气压下,测量v′=1,2,3→v″=0的时间积分荧光强度,结合11Σ+u(v′=1,3)能量辐射率的测量,得到了v′=2→v′=1和v′=2→v′=3的碰撞转移面分别为(1.4±0.5)×10-16cm2,(1.2±0.4)×10-16cm2(对K2+He)和(3.2±1.0)×10-15cm2,(2.6±0.9)×10-15cm2(对K2+H2)。     

应用CASSCF方法精确计算OH分子 A(2)^Σ^(+) 态势能曲线

应用 Gaussian03 程序包中提供的完全活性空间自洽场 (CASSCF) 方法, 采用多种标准基组对 OH 分子A(2)^Σ^(+)态的几何结构进行了优化和势能曲线计算、并将计算结果拟合成了解析的 Murrell-Sorbie 函数。利用得到的解析势能函数进一步计算了该态的光谱常数，并与实验结果进行了比较。此外，本文还给出了一种新的活性空间的选择方法。     

Transition probabilities of the X1Σ+, A1Π, B1Δ, C1Σ+, and D1Π states of the AlO+ cation

ABSTRACT

This study computes the potential energy curves of the X¹Σ⁺, A¹Π, B¹Δ, C¹Σ⁺, and D¹Π states of AlO⁺ cation and the transition dipole moments between them. The orders of the rotationless radiative lifetimes are 10–100?μs for the A¹Π state, 1–1000?ms for the B¹Δ state, 10?ns for the first well and 100?ns for the second well of the C¹Σ⁺ state, and 1?μs for the D¹Π state. Emissions of the B¹Δ–A¹Π and D¹Π–C¹Σ⁺ systems are so weak that they are hardly measured via spectroscopy, the emissions of the C¹Σ⁺–X¹Σ⁺, C¹Σ⁺–A¹Π, and D¹Π–X¹Σ⁺ systems are so strong that they can be detected readily, and emissions of the A¹Π–X¹Σ⁺ and D¹Π–A¹Π systems can be observed through spectroscopy only by a significant effort. There is a strong great similarity between spontaneous emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation and the A²Π–X²Σ⁺ system of the AlO radical. The emissions of the A²Π–X²Σ⁺ system of the AlO radical have been measured in outer space Therefore, it is highly possible that the emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation can be detected in the astrophysical media.     

Kinetics of energy deactivation in the O2(1Δ)-I medium

The kinetics of energy-exchange and quenching processes in the O₂(¹Δ)-I medium plays an important role in the operation of the chemical oxygen-iodine laser. However, up to now, many of the key processes in this medium are not fully understood. In this work, the flow tube technique is used to determine the rate of excitation energy deactivation in the O₂(¹Δ)-I medium in the presence of small concentrations of water and carbon dioxide. The concentrations of electronically excited species are measured with spectrometers calibrated in absolute spectral responsivity. The effective rate constant for the deactivation of O₂(¹Δ) molecules in processes involving iodine atoms is determined. The results are compared to those obtained in previous works.     

Intra-center energy transfer dynamics in Cd1−xMnxTe semi magnetic semiconductors

Intra-center luminescence of Cd_1?xMn_xTe semi magnetic semiconductors under low excitation density was investigated both experimentally and by Monte-Carlo simulation. Experimental time-resolved spectra of 2 eV-band under different photon energy for excitation were used. The approach revealed that Mn²⁺–Mn²⁺excitation energy transfers take place by means of resonant dipole–dipole interaction. Besides energy transfer dynamics is strongly influenced by hopping-assisted quenching. Having been intra-center excitation selective-, mixed- and non-selective types of excitation are proved to occur if photon energy for excitation is increased. This is originated from overlapping of ⁴T₁- and ⁴T₂-states. Under inter-band excitation it was established that Mn²⁺-ion excitation takes place with the aid of excitonic energy transfer, with excitation energy being centered at exciton energy. Under temperature rise the transfer rate vigorously enhances due to great increase of overlap integral of Mn²⁺- ions' side-bands. The quenching is proved to be limited in accordance with existing theory. Inhomogeneous broadening diminishes as a result of fast fluctuation rate of excited ions' energy.     

Line emission and alignment effects in state selective electron transfer in He2+-Li(2s, 2pΣ, 2pΠ) collisions

Classical Trajectory Monte-Carlo (CTMC) method has been used to investigate state selective electron capture by He²⁺ ions colliding with Li(2s) and Li(2p) in as well as alignments in the energy range 1-15 keV/amu. He⁺(4l) electron capture, line emission [He II(n = 4 3)] cross-sections and alignment parameters have been calculated and analyzed in the light of the available results. The undulatory structure of the capture and emission cross-sections have been explained qualitatively in terms of a quasi-molecular ion formation. Projectile impact energy and spatial overlap play crucial role in determining the alignment effects. Received 3 July 1998 and Received in final form 3 June 1999     

Accurate potential energy function and spectroscopic study of the X~2Σ~+,A~2Ⅱ and B~2Σ~+ states of the CP radical

This paper calculates the equilibrium internuclear separations,the harmonic frequencies and the potential energy curves of the X 2 Σ +,A 2Ⅱ and B 2 Σ + states of the CP radical by the highly accurate valence internally contracted multireference configuration interaction method with correlation-consistent basis sets(aug-cc-pV6Z for C atom and aug-cc-pVQZ for P atom).The potential energy curves are all fitted with the analytic potential energy function by the least-square fitting.Employing the analytic potential energy function,we determine the spectroscopic constants(B e,α e and ω e χ e) of these states.For the X 2 Σ + state,the obtained values of D e,B e,α e,ω e χ e,R e and ω e are 5.4831 eV,0.792119 cm 1,0.005521 cm 1,6.89653 cm 1,0.15683 nm,12535.11 cm 1,respectively.For the A 2Ⅱ state,the present values of D e,B e,α e,ω e χ e,R e and ω e are 4.586 eV,0.703333 cm 1,0.005458 cm 1,6.03398 cm 1,0.16613 nm,1057.89 cm 1,respectively.For the B 2 Σ + state,the present values of D e,B e,α e,ω e χ e,R e and ω e are 3.506 eV,0.677561 cm 1,0.00603298 cm 1,5.68809 cm 1,0.1696 nm,822.554 cm 1,respectively.For these states,the vibrational states with the rotational quantum number J equals zero(J = 0) are studied by solving the radial nuclear Schro¨dinger equation using the Numerov method.For each vibrational state,the vibrational level,the classical turning points,the rotational inertial and the centrifugal distortion constants are calculated.Comparison is made with recent theoretical and experimental results.