High-precision laser and RF spectroscopy of the spin-rotation and HFS interactions in the X2Σ+ and B2Σ+ states of LaO

The spin-rotation and hyperfine interactions in the X²Σ⁺ and B²Σ⁺ electronic states of ¹³⁹La¹⁶O have been studied using Doppler-free laser-induced fluorescence and molecular-beam laser-rf double resonance. Observations were made for several values of v and many values of N, allowing evaluation of the principal interaction strengths and their N and v dependences for both the X and B states. The results are compared with earlier results for the isoelectronic system ¹³⁷Ba¹⁹F.     

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.     

High resolution emission spectroscopy of the E2Π–X2Σ+ transition of SrH and SrD

Emission spectra of SrH and SrD have been studied at high resolution using a Fourier transform spectrometer. The molecules have been produced in a high temperature furnace from the reaction of strontium metal vapor with H₂/D₂ in the presence of a slow flow of Ar gas. The spectra observed in the 18 000–19 500 cm^?1 region consist of the 0–0 and 1–1 bands of the E²Π–X²Σ⁺ transition of the two isotopologues. A rotational analysis of these bands has been obtained by combining the present measurements with previously available pure rotation and vibration–rotation measurements for the ground state, and improved spectroscopic constants have been obtained for the E²Π state. The present analysis provides spectroscopic constants for the E²Π state as ΔG(½) = 1166.1011(15) cm^?1, B_e = 3.805503(32) cm^?1, α_e = 0.098880(47) cm^?1, r_e = 2.1083727(89) Å for SrH, and ΔG(½) = 839.1283(23) cm^?1, B_e = 1.918564(15) cm^?1, α_e = 0.034719(23) cm^?1, r_e = 2.1121943(83) Å for SrD.     

State selective predissociation spectroscopy of hydrogen chloride ions (HCl+) via the A2Σ+ ← X2Π3/2 transition

The photodissociation of hydrogen chloride ions (HCl⁺) has been investigated through the A²Σ⁺ (ν′ = 6, 7 and 8) ← X ²Π_3/2 (ν″ = 0) transition. The spectra reveal that state selective photodissociation with complete resolution of the spin, orbital, and rotational angular momentum is possible in the A ²Σ⁺ (ν′ = 6) state. The analysis of these spectra yields the rotational and the spin-rotation coupling constant of the A ²Σ⁺ (ν′ = 6) state. The lifetime of HCl⁺ decreases significantly with increasing vibrational excitation in the ²Σ⁺ state. Within the experimental error limits no J dependence of the lifetime is observerd. The state selective photodissociation of the HCl⁺ ions is also shown to be a very sensitive probe for unexpected parity transitions in the 2 + 1 REMPI formation of the HCl⁺ ions in the X 2Π_3/2 (ν″ = 0) state.     

High-resolution laser excitation spectroscopy: Analysis of the B2Σ+-X2Σ+ system of CaCl

Single-mode cw dye laser excitation spectra of the (0, 0), (1, 1), and (2, 2) bands of the B²Σ⁺-X²Σ⁺ system of CaCl have been observed and assigned. Some 300 independent photo-luminescence spectra have been used in making the rotational assignment and demonstrate the power of the technique of line-by-line analysis in unraveling complex spectra. Spectroscopic constants (cm^?1) obtained from a weighted least squares fit of the data are given below. Numbers in parentheses refer to 95% confidence limits in the last digit.

     

6.

Simulation of the Ã2Σ+–X̃2Π absorption and emission spectra of the SiCCl radical     

Alexander O. Mitrushchenkov  Vincent Brites 《Molecular physics》2015,113(13-14):1695-1703

     

7.

Emission bands of AIH (X1Σ+): The 2-0 sequence     

《Journal of Molecular Spectroscopy》1987,125(1):115-121

Seven bands of the 2-0 sequence of AlH in its X¹Σ⁺ ground state have been observed in emission from a carbon furnace and recorded with a Bomem interferometer. Improved values for the molecular constants have been obtained. The principal constants are B_e = 6.3937(4), α₃ = 0.1868(3), 10⁴D_e = 3.683(10), ω_e = 1682.43, and ω_eχ_e = 29.11 cm⁻¹, where the error limits are 3σ. Possibilities for observing AlH in astrophysical sources are discussed.     

8.

Molecular constants of LiCl(X~1Σ~+) and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures          下载免费PDF全文

朱遵略  张小妞  寇素华  施德恒  孙金锋 《中国物理 B》2010,19(11):113602-113602

Interaction potentials for LiCl(X 1 Σ +) are constructed by the highly accurate valence internally contracted mul-tireference configuration interaction in combination with a number of large correlation-consistent basis sets,which are used to determine the spectroscopic parameters (D 0,D e,R e,ω e,ω e χ e,B e and α e).The potentials obtained at the basis sets,i.e.,aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li,are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0×10 12 to 1.0×10 4 a.u.The derived total elastic cross sections are very large and almost constant at ultralow temperatures,and their shapes are mainly dominated by the s-partial wave at very low impact energies.Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime,which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves.Abundant resonances exist for the elastic partial-wave cross sections until l=22 partial waves.The vibrational manifolds of the LiCl(X 1 Σ +) molecule,which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl,should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.     

9.

Production of projectile and target-vacancy in near-symmetric collisions of 60–100 MeV Cu~(9+) ions with thin Zn target          下载免费PDF全文

《中国物理 B》2016,(3)

We report studies on both target and projectile K-shell ionization by collisions of Cu~(9+)ions on the thin Zn target in the energy range of 60–100 Me V. In this work, the relative ratio for the production of the target to projectile K-vacancy is measured. The result shows that it almost remains stable over this energy range and has good consistency with the predictions by vacancy transfer via the 2pσ–1sσ rotational coupling, which gives experimental evidence for K-vacancy sharing between two partners. Furthermore, the discussion for comparisons between the experimental ionization cross sections and the possible theoretical estimations is presented. These comparisons suggest that the experimental data agree well with those predicted by the Binary–Encounter approximation(BEA) model but are not in good agreement with the modified BEA calculations. It allows us to infer that the direct ionization(and/or excitation) is of importance to initial K-vacancy production before 2pσ–1sσ transitions in the present collision condition.     

10.

Combination transitions due to stretching and librations of OH⁻ ions in LiNbO₃     

Kovács L  Lengyel K  Szalay V 《Optics letters》2011,36(18):3714-3716

A new absorption band has been detected at 4009 cm?1 in stoichiometric LiNbO? single crystals. Based on present and earlier experiments and recent calculations, this band has been assigned as a combination transition involving the OH stretching and an OH librational mode. The librational mode participating in this combination is of lower fundamental frequency than that contributing to the combination band at 4415 cm1 observed by Gr?ne and Kapphan [J. Phys. Condens. Matter 7, 3051 (1995)].     

11.

A quasiclassical study of collisions of He with HD(B 1Σ+ u )     

Stavros C. Farantos 《Molecular physics》2013,111(4):835-845

A quasiclassical trajectory study has been carried out for collisions of ⁴He with electronically excited H₂(B ¹Σ⁺ _u ) and its isotopomer HD. By using analytical fits for the ab initio potential energy surfaces of the ground and the excited state we have obtained vibrational and electronic quenching cross sections for several initial conditions. We draw the following conclusions. Vibrational excitation strongly promotes electronic quenching whereas translational energy is less effective. Rotational excitation decreases the rate of quenching. In a remarkable contrast to the ground electronic state, vibrational energy transfer on the excited potential energy surface is an efficient and fast process. Collisions at high energies results in T → R energy transfer. The above conclusions are valid for both H₂ and HD.     

12.

Ab initio configuration interaction study on the electronic structure of the X2Σ+, B2Σ+ and 32Σ+ states of SiO+     

NOBUMITSU HONJOU 《Molecular physics》2013,111(1-2):131-141

The energy levels and electronic structure of the X²Σ⁺, B²Σ⁺ and 3²Σ⁺ states of SiO⁺ are studied using ab initio configuration interaction (CI) calculations at and around their equilibrium internuclear distances R _e. Spectroscopic constants and the vertical excitation energy from the SiO⁺ X²Σ⁺ state are predicted for the 3²Σ⁺ state. Based on the calculated CI wavefunctions, avoided crossings of the potential energy curve for the 3²Σ⁺ state and a near-degeneracy effect in the avoided crossing region are examined. The effects of the mixing of excited configuration state functions in the total electronic wavefunctions for the 1–3 ²Σ⁺ states are investigated by analysing correlation energies in terms of the contributions from classes of excited configurations. The importance of both the near-degeneracy effect and the correlation energy effect in describing correctly the electronic structure of the 3 ²Σ⁺ state in the neighbourhood of its R _e is discussed.     

13.

Spectroscopic parameters and molecular constants of HI(X~1Σ~+),DI(X~1Σ~+) and TI(X~1Σ~+) isotope molecules          下载免费PDF全文

张小妞  施德恒  朱遵略  孙金锋 《中国物理 B》2010,19(12):123501-123501

The potential energy curve (PEC) of HI(X¹Σ⁺) molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEC of HI(X¹Σ⁺), the spectroscopic parameters of three isotopes, HI(X¹Σ⁺), DI(X¹Σ⁺) and TI(X¹Σ⁺), are determined in the present work. For the HI(X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm^-1, 40.0703 cm^-1, 0.1699 cm^-1 and 6.4373 cm^-1, respectively; for the DI (X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm^-1, 20.8581 cm^-1, 0.0611 cm^-1 and 3.2468 cm^-1, respectively; for the TI (X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm^-1, 14.0765 cm^-1, 0.0338 cm^-1 and 2.1850 cm^-1, respectively. These results accord well with the available experimental results. With the PEC of HI(X¹Σ⁺) molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero (J = 0). For each vibrational state, vibrational level G(?), inertial rotation constant B_? and centrifugal distortion constant D_? are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.     

14.

Laser-induced fluorescence decay lifetimes of shock-heated NO (A 2Σ+)     

U. E. Meier  G. A. Raiche  D. R. Crosley  G. P. Smith  D. J. Eckstrom 《Applied physics. B, Lasers and optics》1991,53(3):138-141

Radiative emission in the NO -band system occurs when air at a few Torr initial pressure is shock-heated at sufficiently high temperatures of 3500–7000 K. Emission spectra of this system in shocks indicate that collisional quenching of the emitting A ²⁺ state is a critical quantity controlling the intensity. Quenching of excited NO by NO itself has been measured using direct time decay of laser-induced fluorescence in the shock tube at 3500 K. The cross section (2– error) is 59±20 Ų, compared to the room temperature value 37±8 Ų. At 3500 K, N₂ also quenches NO with a cross section 2 Ų, much larger than the value at 300 K.Sabbatical visitor, on leave from DLR Stuttgart, Fed. Rep. Germany     

15.

Anisotropic emission of charged mesons and structure characteristic of emission source in heavy ion collisions at 1-2A GeV          下载免费PDF全文

刘福虎 《中国物理 B》2008,17(3):883-895

Angular distributions of pious and kaons produced in heavy ion collisions at the low-energy end of high energies （1-2 A GeV） have been investigated by using a multisource ideal gas model. The model covers the expansions and movements of the emission sources, and it is related to the collective flows. By using the analytic expression and the Monte Carlo method, the azimuthal and polar angle distributions of mesons are calculated by the model and compared with the experimental data of the KaoS Collaboration.     

16.

The ion-molecule reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the predissociation of the A2Σ+ and B2Π states of N2O+     

G. CHAMBAUD  H. GRITLI  P. ROSMUS  H.-J. WERNER  P. J. KNOWLES 《Molecular physics》2013,111(21):1793-1802

The potential energy surfaces (PESs) for several electronic states involved in the reaction O⁺ (⁴S) + N₂(X¹Σ⁺) → NO⁺ (X¹Σ ⁺, v′) + N(⁴S) and the role of the ionic N₂O⁺ intermediate have been investigated by ab initio calculations. The ⁴A″ PES, which correlates with the ground state educts, has a barrier of about 1 eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X² Π electronic ground state of the N₂O⁺ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1 eV, the reaction proceeds mainly on the adiabatic PES of the ⁴A″ state. The A²Σ⁺ state of N₂O⁺ predissociates via a vibronic coupling with the B²Π state, and in bent structures via a spin-orbit coupling with the ⁴A″ component of the ⁴II state. The electronic structure of the B²Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N₂O⁺.     

17.

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

A. N. Perumal  D. N. Tripathi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):169-176

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     

18.

2-μm emission performance of Tm~(3+)-Ho~(3+) co-doped tellurite glasses     

王孟  汪国年  衣丽霞  李顺光  胡丽丽  张军杰 《中国光学快报(英文版)》2010,(1)

The emission properties of 2-μm region fluorescence of Tm~(3+)-Ho~(3+) co-doped tellurite glasses are investigated. Introducing F~- ions to the composition of tellurite glasses plays a positive effect on the 2-μm emission.A maximum intensity of 2-μm emission is achieved when 1.5-mol%Tm_2O_3 and l-mol% Ho_2_O3 concentration are doped in the glasses.The emission cross section and gain coefficient of the ~5I_8→~5I_7 transition of Ho~(3+) are calculated.The emission cross section has a maximum of 1.29×10~(-2...     

19.

The vibrational structure of bromocyanoacetylene cation in the X̃2π and Ã2π electronic states studied by emission and laser exci     

《Journal of Electron Spectroscopy and Related Phenomena》1986,41(2):265-274

The vibrational frequencies of bromocyanoacetylene cation in its ground and first excited electronic states have been obtained by recording and analysing the emission and laser excitation spectra of the òπ-X̃²π transition. In the emission experiments the ions are produced rotationally cooled to ca. 10 K by means of a supersonic free jet and in the laser excitation measurements to ca. 100 K by Penning ionisation followed by collisional relaxation. The resulting narrowing of the vibronic bands in the spectra is such that the vibrational frequencies of most of the fundamentals could be inferred to within ± 2 cm⁻¹.     

20.

A comparison of finite basis set and finite difference Hartree—Fock calculations for the open-shell (X 2Σ+) molecules BaF and YbF     

J. KOBUS  D. MONCRIEFF  S. WILSON 《Molecular physics》2013,111(4):499-508

A comparison is made of the accuracy with which the total electronic energy can be calculated by using the finite basis set approach (the algebraic approximation) and the finite difference method in calculations employing the Hartree—Fock model for the open shell ground (X ²Σ⁺) states of the fluorides BaF and YbF. The convergence of the calculations carried out within the algebraic approximation is monitored by employing systematically constructed basis sets of increasing size. The difference between the finite basis set and finite difference Hartree—Fock energies is 2.6μE _h for BaF and 2.8μE _h for YbF. Dipole moments determined within the algebraic approximation are also compared with the corresponding finite difference expectation values.     

	$\text{X}{}^2\text{Σ}{}^{\mathrm{+}}$	$\text{B}{}^2\text{Σ}{}^{\mathrm{+}}$
$\text{T}{}_{\mathrm{e}}$	0	16856.69(2)
$\text{ω}{}_{\mathrm{e}}$	369.8(10)	366.8(10)
$\text{ω}{}_{\mathrm{e}}\text{x}{}_{\mathrm{e}}$	1.13(20)	1.28(20)
$\text{B}{}_{\mathrm{e}}$	0.15200(54)	0.15448(54)
$\text{α}{}_{\mathrm{e}}$	0.00063(34)	0.00073(35)
$\text{D}{}_{\mathrm{e}}$	1.027(16) × 10?7	1.097(17) × 10?7
$\text{γ}{}_{\mathrm{e}}$ (spin-rotation)	+0.003	?0.0630(16)

Emission bands of AIH (X1Σ+): The 2-0 sequence

Seven bands of the 2-0 sequence of AlH in its X¹Σ⁺ ground state have been observed in emission from a carbon furnace and recorded with a Bomem interferometer. Improved values for the molecular constants have been obtained. The principal constants are B_e = 6.3937(4), α₃ = 0.1868(3), 10⁴D_e = 3.683(10), ω_e = 1682.43, and ω_eχ_e = 29.11 cm⁻¹, where the error limits are 3σ. Possibilities for observing AlH in astrophysical sources are discussed.     

Molecular constants of LiCl(X~1Σ~+) and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures

Interaction potentials for LiCl(X 1 Σ +) are constructed by the highly accurate valence internally contracted mul-tireference configuration interaction in combination with a number of large correlation-consistent basis sets,which are used to determine the spectroscopic parameters (D 0,D e,R e,ω e,ω e χ e,B e and α e).The potentials obtained at the basis sets,i.e.,aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li,are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0×10 12 to 1.0×10 4 a.u.The derived total elastic cross sections are very large and almost constant at ultralow temperatures,and their shapes are mainly dominated by the s-partial wave at very low impact energies.Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime,which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves.Abundant resonances exist for the elastic partial-wave cross sections until l=22 partial waves.The vibrational manifolds of the LiCl(X 1 Σ +) molecule,which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl,should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.     

Production of projectile and target-vacancy in near-symmetric collisions of 60–100 MeV Cu~(9+) ions with thin Zn target

We report studies on both target and projectile K-shell ionization by collisions of Cu~(9+)ions on the thin Zn target in the energy range of 60–100 Me V. In this work, the relative ratio for the production of the target to projectile K-vacancy is measured. The result shows that it almost remains stable over this energy range and has good consistency with the predictions by vacancy transfer via the 2pσ–1sσ rotational coupling, which gives experimental evidence for K-vacancy sharing between two partners. Furthermore, the discussion for comparisons between the experimental ionization cross sections and the possible theoretical estimations is presented. These comparisons suggest that the experimental data agree well with those predicted by the Binary–Encounter approximation(BEA) model but are not in good agreement with the modified BEA calculations. It allows us to infer that the direct ionization(and/or excitation) is of importance to initial K-vacancy production before 2pσ–1sσ transitions in the present collision condition.     

Combination transitions due to stretching and librations of OH⁻ ions in LiNbO₃

A new absorption band has been detected at 4009 cm?1 in stoichiometric LiNbO? single crystals. Based on present and earlier experiments and recent calculations, this band has been assigned as a combination transition involving the OH stretching and an OH librational mode. The librational mode participating in this combination is of lower fundamental frequency than that contributing to the combination band at 4415 cm1 observed by Gr?ne and Kapphan [J. Phys. Condens. Matter 7, 3051 (1995)].     

A quasiclassical study of collisions of He with HD(B 1Σ+ u )

A quasiclassical trajectory study has been carried out for collisions of ⁴He with electronically excited H₂(B ¹Σ⁺ _u ) and its isotopomer HD. By using analytical fits for the ab initio potential energy surfaces of the ground and the excited state we have obtained vibrational and electronic quenching cross sections for several initial conditions. We draw the following conclusions. Vibrational excitation strongly promotes electronic quenching whereas translational energy is less effective. Rotational excitation decreases the rate of quenching. In a remarkable contrast to the ground electronic state, vibrational energy transfer on the excited potential energy surface is an efficient and fast process. Collisions at high energies results in T → R energy transfer. The above conclusions are valid for both H₂ and HD.     

Ab initio configuration interaction study on the electronic structure of the X2Σ+, B2Σ+ and 32Σ+ states of SiO+

The energy levels and electronic structure of the X²Σ⁺, B²Σ⁺ and 3²Σ⁺ states of SiO⁺ are studied using ab initio configuration interaction (CI) calculations at and around their equilibrium internuclear distances R _e. Spectroscopic constants and the vertical excitation energy from the SiO⁺ X²Σ⁺ state are predicted for the 3²Σ⁺ state. Based on the calculated CI wavefunctions, avoided crossings of the potential energy curve for the 3²Σ⁺ state and a near-degeneracy effect in the avoided crossing region are examined. The effects of the mixing of excited configuration state functions in the total electronic wavefunctions for the 1–3 ²Σ⁺ states are investigated by analysing correlation energies in terms of the contributions from classes of excited configurations. The importance of both the near-degeneracy effect and the correlation energy effect in describing correctly the electronic structure of the 3 ²Σ⁺ state in the neighbourhood of its R _e is discussed.     

Spectroscopic parameters and molecular constants of HI(X~1Σ~+),DI(X~1Σ~+) and TI(X~1Σ~+) isotope molecules

The potential energy curve (PEC) of HI(X¹Σ⁺) molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEC of HI(X¹Σ⁺), the spectroscopic parameters of three isotopes, HI(X¹Σ⁺), DI(X¹Σ⁺) and TI(X¹Σ⁺), are determined in the present work. For the HI(X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm^-1, 40.0703 cm^-1, 0.1699 cm^-1 and 6.4373 cm^-1, respectively; for the DI (X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm^-1, 20.8581 cm^-1, 0.0611 cm^-1 and 3.2468 cm^-1, respectively; for the TI (X¹Σ⁺), the values of D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm^-1, 14.0765 cm^-1, 0.0338 cm^-1 and 2.1850 cm^-1, respectively. These results accord well with the available experimental results. With the PEC of HI(X¹Σ⁺) molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero (J = 0). For each vibrational state, vibrational level G(?), inertial rotation constant B_? and centrifugal distortion constant D_? are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.     

Laser-induced fluorescence decay lifetimes of shock-heated NO (A 2Σ+)

Radiative emission in the NO -band system occurs when air at a few Torr initial pressure is shock-heated at sufficiently high temperatures of 3500–7000 K. Emission spectra of this system in shocks indicate that collisional quenching of the emitting A ²⁺ state is a critical quantity controlling the intensity. Quenching of excited NO by NO itself has been measured using direct time decay of laser-induced fluorescence in the shock tube at 3500 K. The cross section (2– error) is 59±20 Ų, compared to the room temperature value 37±8 Ų. At 3500 K, N₂ also quenches NO with a cross section 2 Ų, much larger than the value at 300 K.Sabbatical visitor, on leave from DLR Stuttgart, Fed. Rep. Germany     

Anisotropic emission of charged mesons and structure characteristic of emission source in heavy ion collisions at 1-2A GeV

Angular distributions of pious and kaons produced in heavy ion collisions at the low-energy end of high energies （1-2 A GeV） have been investigated by using a multisource ideal gas model. The model covers the expansions and movements of the emission sources, and it is related to the collective flows. By using the analytic expression and the Monte Carlo method, the azimuthal and polar angle distributions of mesons are calculated by the model and compared with the experimental data of the KaoS Collaboration.     

The ion-molecule reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the predissociation of the A2Σ+ and B2Π states of N2O+

The potential energy surfaces (PESs) for several electronic states involved in the reaction O⁺ (⁴S) + N₂(X¹Σ⁺) → NO⁺ (X¹Σ ⁺, v′) + N(⁴S) and the role of the ionic N₂O⁺ intermediate have been investigated by ab initio calculations. The ⁴A″ PES, which correlates with the ground state educts, has a barrier of about 1 eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X² Π electronic ground state of the N₂O⁺ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1 eV, the reaction proceeds mainly on the adiabatic PES of the ⁴A″ state. The A²Σ⁺ state of N₂O⁺ predissociates via a vibronic coupling with the B²Π state, and in bent structures via a spin-orbit coupling with the ⁴A″ component of the ⁴II state. The electronic structure of the B²Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N₂O⁺.     

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     

2-μm emission performance of Tm~(3+)-Ho~(3+) co-doped tellurite glasses

The emission properties of 2-μm region fluorescence of Tm~(3+)-Ho~(3+) co-doped tellurite glasses are investigated. Introducing F~- ions to the composition of tellurite glasses plays a positive effect on the 2-μm emission.A maximum intensity of 2-μm emission is achieved when 1.5-mol%Tm_2O_3 and l-mol% Ho_2_O3 concentration are doped in the glasses.The emission cross section and gain coefficient of the ~5I_8→~5I_7 transition of Ho~(3+) are calculated.The emission cross section has a maximum of 1.29×10~(-2...     

The vibrational structure of bromocyanoacetylene cation in the X̃2π and Ã2π electronic states studied by emission and laser exci

The vibrational frequencies of bromocyanoacetylene cation in its ground and first excited electronic states have been obtained by recording and analysing the emission and laser excitation spectra of the òπ-X̃²π transition. In the emission experiments the ions are produced rotationally cooled to ca. 10 K by means of a supersonic free jet and in the laser excitation measurements to ca. 100 K by Penning ionisation followed by collisional relaxation. The resulting narrowing of the vibronic bands in the spectra is such that the vibrational frequencies of most of the fundamentals could be inferred to within ± 2 cm⁻¹.     

A comparison of finite basis set and finite difference Hartree—Fock calculations for the open-shell (X 2Σ+) molecules BaF and YbF

A comparison is made of the accuracy with which the total electronic energy can be calculated by using the finite basis set approach (the algebraic approximation) and the finite difference method in calculations employing the Hartree—Fock model for the open shell ground (X ²Σ⁺) states of the fluorides BaF and YbF. The convergence of the calculations carried out within the algebraic approximation is monitored by employing systematically constructed basis sets of increasing size. The difference between the finite basis set and finite difference Hartree—Fock energies is 2.6μE _h for BaF and 2.8μE _h for YbF. Dipole moments determined within the algebraic approximation are also compared with the corresponding finite difference expectation values.