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1.
In a magnetic field, Cs2 molecules were excited from the ground X1Σ+g(vX=0,JX=55) level to the D 1Σ+u(v=46,J=54) level by dissociation laser light linearly polarized parallel to the field, for which the magnetic sublevels were degenerated and thus all the transitions between them were simultaneously stimulated. Probe laser light excited the dissociated Cs 6p2P3/2 atomic fragments to 6p2D3/2 level and the resultant 6p2P1/2 - 6d2D3/2 emission was detected as the function of the wavelength of the probe light. The populations of the 6p2P3/2,mj magnetic sublevels were determined from the relative strengths of the 6p2P3/2,mj - 6d2D3/2,m'j transitions induced by the probe light. Non-zero orientation O0 was found in the ensemble of dissociated Cs 6p2P3/2 atomic fragments. The orientation O0 increased as the magnetic field strength increased. It was demonstrated both experimentally and theoretically that the orientation O0 was induced through the interference in the excitation and dissociation paths in the presence of an external magnetic field, even when all degenerated transitions between the magnetic sublevels of the molecules are simultaneously excited by the light linearly polarized parallel to the field.  相似文献   

2.
Based on the potential energy surface reported by Li and co-workers (J. Comput. Chem. 34 1686–1696 (2013)), the dynamics calculations of N(2D)?+?H2(v 0?=?0, j 0?=?0) reaction and its isotopic variants HD and D2 are studied using time-dependent wave packet method in the collision energy range of 0.01–1.0?eV. Dynamics properties such as reaction probability, differential cross section, and integral cross section are studied at state-to-state level of theory. Present values are compared with available theoretical and experimental results. The results indicate that the integral cross sections of N(2D)?+?D2 reaction are in general good agreement with the experimental data at collision energy below 0.15?eV. The rotational state-resolved integral cross sections of N(2D)?+?H2/HD/D2 reactions are compared with experimental values for the first time, with the obtained values being in good agreement with the experimental data.  相似文献   

3.
New measurements of the photoionization cross sections from the 4p 2P1/2,3/2, 5d 2D5/2,3/2 and 7s 2S1/2 excited states of potassium are presented. The cross sections have been measured by two-step excitation and ionization using a Nd:YAG laser in conjunction with a thermionic diode ion detector. By applying the saturation technique, the absolute values of the cross sections from the 4p 2P3/2 and 4p 2P1/2 states at 355 nm are determined as 7.2±1.1 and 5.6±0.8 Mb, respectively. The photoionization cross section from the 5d 2D5/2,3/2 excited state has been measured using two excitation paths, two-step excitation and two-photon excitation from the ground state. The measured values of the cross sections from the 5d 2D5/2 state by two-photon excitation from the ground state is 28.9±4.3 Mb, whereas in the two-step excitation, the cross section from the 5d 2D3/2 state via the 4p 2P1/2 state and from the 5d 2D5/2,3/2 states via the 4p 2P3/2 state are determined as 25.1±3.8 and 30.2±4.5 Mb, respectively. Besides, we have measured the photoionization cross sections from the 7s 2S1/2 excited state using the two-photon excitation from the ground state as 0.61±0.09 Mb.  相似文献   

4.
Differential scattering cross sections in the energy rangeE CM=25–50 eV have been measured in a crossed beam machine for the scattering of Na+ by laser excited Na(32 P 3/2). The superelastically scattered ions resulting from the collisional deexcitation process 32 P 3/2-2 S 1/2 are sharply peaked at a constant reduced scattering angle of 180eV degrees. Through the choice of either linearly or circularly polarized light, one can selectively excite the magnetic sublevels of the Na atoms. This ability to align or orient the Na* allows us to discuss in considerable detail both the transition from the space-fixed (atomic) to the body-fixed (molecular) system and the dynamics in the merging region of the two frames. We find that the symmetry axis of the excited electron charge cloud is locked to the internuclear axis and hence to the body-fixed reference frame at an internuclear separation of about 35 a.u. A pronounced asymmetry of the scattering from atoms excited with LHC or RHC polarized light is discussed in terms of simple models.  相似文献   

5.
H+ impact single and He2+ impact single and double electron capture cross sections of magnesium atoms have been calculated in the modified binary encounter approximation (BEA). The accurate expressions of ion impact sDE\sigma _{\Delta {E}} (cross section for energy transfer DE\Delta E) and Hartree-Fock momentum distributions of the target electrons have been used throughout the calculations. On the basis of the present work it is concluded that inner shell captures by H+ and He2+ ions incident on magnesium atoms contribute partly to single electron capture and partly to transfer ionization cross sections. The calculated He2+ impact double electron capture cross sections of magnesium are in reasonably good agreement with the experimental observations. This indicates the success of the present theoretical approach in study of charge transfer cross sections of atoms as indirect mechanisms do not interfere with double electron capture processes in this case.  相似文献   

6.
Slow ion production cross sections for collisions of H+3 and D+3 ions with H2 and D2 have been measured at collision energies between 100 eV and 500 eV. The values vary from 2 × 10-17 cm2 to 6 × 10-17 cm2. The smaller cross sections for D3 projectiles may be explained as an internal energy effect.  相似文献   

7.
We have investigated the isotope effect for electron capture into the 2S-state of hydrogen in close collisions for the processes H+ in H2 and H+ in D2. The differential cross sections and transition probabilities P2S obtained for capture into H(2S) as a function of energy at a fixed angle of θ = 1° exhibit distinctive features, but no apparent isotope effects are detected.  相似文献   

8.
Using the method of coupled channels to incorporate NΔ intermediate states into the reaction p + p → d + π+ we calculate the differential cross sections, when both the beam and the target are polarized. The results for yy-polarized initial state are given in some detail at 580 MeV. We propose the use of the differential cross section with initial longitudinal polarizations to investigate the D-state probability of the deuteron, PD. This quantity is found to be very sensitive to PD.  相似文献   

9.
The spin-polarization of the optically pumped Na-groundstate is investigated in presence of the stable He- and H2-isotopes. The following disorientation cross sections are derived from the pressure dependence of the relaxation rate:σ=(16.2±2.0) · 10?26 cm2 for He3 σ=(2.4±0.5) · 10?26 cm2 for He4 σ=(3.9±1.5) · 10?26 cm2 for H2 σ=(2.3±1.0) · 10?26 cm2 for D2. These values can be compared with theoretical cross sections based on two relaxation models and indicate the existence of a relaxation mechanism involving the exchange of the electronic alkali-spin with the nuclear spin of the foreign gas.  相似文献   

10.
This paper presents a new proposal for a mutually pumped phase conjugate mirror (MPPCM) using cross polarization. In the cross polarized MPPCM, two light beams, whose polarizations are orthogonal to each other, incident on a photorefractive crystal, causing photorefractive interaction to generate phase conjugate waves with an orthogonal polarization to an incident beam. The use of Ar+ laser and BaTiO3 crystal in an experiment for the cross polarized MPPCM found that diffraction efficiency for an extraordinary beam is about 20%. As opposed to a conventional parallel polarized MPPCM in which the use of a beam splitter is required to separate a diffraction beam, the cross polarized MPPCM can efficiently extract phase conjugate waves by means of a polarized beam splitter, demonstrating the advantage of substantially improved efficiency.  相似文献   

11.
It is found in an experiment with narrowband laser pumping of Cs atoms by light of the D 2-line that the spectral dependence of the polarization of atoms significantly differs from the spectral dependence of the light absorption by nonpolarized atoms. The difference lies in a partial resolution of the hyperfine structure of the excited 62 P 3/2 state, which remains unresolved in the case of nonpolarized atoms. The shape of the spectral dependence of the atom polarization observed upon pumping with circularly polarized light differs from that in the case of the linear polarized pumping and depends strongly on the buffer gas pressure, which allows one to obtain experimental information on collisional relaxation in the excited state. Calculation for a cell with antirelaxation coating and a cell with helium (6-Torr pressure) gives spectral dependences that are qualitatively consistent with experiment.  相似文献   

12.
The Classical Trajectory Monte Carlo (CTMC) Method has been used to calculate the differential, partial and total single electron capture cross sections for the collision of H+/D+ with Ca and Mg atoms in the energy range of 1–100 keV. The differential cross sections at angles near the diffraction limit (<0.1) in both systems show a forward peak followed by an asymptotic fall at higher angles. Total and partial capture cross sections are found to be in good agreement with the experimental observations. Oscillations in the partial capture cross sections have been explained due to the swapping of the field electron. Isotope effect in the electron transfer is reported to be negligible.  相似文献   

13.
The dependence of the electronic transition moment on the internuclear distance is explicitly taken into account in the calculation of the photoionization cross section. Thus, the partial ionization cross sections for producing different vibrational states of the residual ion are obtained without invoking the Franck-Condon factor approximation. The exact electrostatic potential of H2+, as well as the two-center Coulomb field, is used in the evaluation of the continuum wave function. The result can explain fairly well the ratios of the partial cross sections measured at 584 Å. The effect of the polarization of H2+ due to the departing photoelectron is also studied and found to be small as far as the relative cross section is concerned. The total photoionization cross sections of H2 and D2 are compared with previous results obtained by other authors.  相似文献   

14.
We present experimentally measured absolute values of the photoionization cross sections from the 5s5p 1P1 and 5s5p 3P1 excited states of strontium at the first ionization threshold as 11.4±1.8 Mb and 10.7±1.7 Mb respectively using saturated absorption technique along with a thermionic diode ion detector in conjunction with a Nd:YAG pumped dye laser system. These threshold photoionization cross sections values have been utilized to determine the oscillator strengths of the 5s5p 1P1↦5snd 1D2 and 5s5p 3P1↦5snd 3D2 Rydberg transitions. The oscillator strength densities in the continuum corresponding to the 5s5p 3P1 excited state have also been determined by measuring the photoionization cross sections at five ionizing wavelengths above the first ionization threshold. Smooth merging of the discrete f-values into the oscillator strength densities has been observed for the 5s5p 3P1↦5snd 3D2 series across the ionization threshold.  相似文献   

15.
We report desorption cross section measurements for one monolayer of chemisorbed carbon on a Mo(1 0 0) surface induced by sputtering with noble gas ions (Ne+, Ar+, Xe+) at different incident angles, ion energies, and substrate temperatures. Desorption cross sections were determined by using low-energy ion scattering (LEIS) to monitor the increase of the signal from the Mo substrate. A monolayer of p(1 × 1) carbon adatoms on the Mo(1 0 0) surface was created by dosing ethylene (C2H4) to the substrate at 800 K, and characterized by Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). We find that the carbon desorption cross section increases with increasing mass and energy of the impinging ions, and there is a maximum value for the desorption cross section at an incident angle for the ions of 30° from the surface plane. The desorption cross section also increases up to a substrate temperature of 300 °C. Values for the carbon desorption cross section for carbon adatoms on Mo(1 0 0) by 400-eV Xe+ ion sputtering are about 2 × 10−15 cm2, which is one order of magnitude higher than those for bulk carbon samples. This information is particularly important for evaluation of ion-engine lifetimes from ground-test measurements in which contaminant carbon is deposited on Mo accelerator grids, potentially altering the sputtering rate of the Mo. Our measurements show that monolayer amounts of carbon on Mo have desorption cross sections that are two orders of magnitude higher than estimates of what would be required to reduce the Mo erosion rate, and thus ground-test measurements can be used with confidence to predict ion-engine wear in space, from this perspective.  相似文献   

16.
使用密耦近似(Close-Coupling)方法、采用Tang-Toennies势模型计算了惰性气体原子Ne与H2分子及同位素D2分子在碰撞能量为83.8 meV时的微分散射截面及分波截面, 并与实验值和文献值进行比较.计算得到的微分散射截面值与实验值符合得较好,分波截面值与文献值也相符合.使用同样的方法和模型,文中对Ne-H2(D2,T2)三个体系的微分截面和分波截面进行了系统计算和比较分析,得出对称同位素替代碰撞体系的散射截面规律.  相似文献   

17.
The characteristic angles and cross sections for a (\mathop 1- 0) + (\mathop 1- 1)(\mathop 1\limits^ - 0) + (\mathop 1\limits^ - 1) reaction in which H atoms with an energy of 0.1–10 000 MeV lose electrons when scattered on C, N, or O atoms were calculated for the relativistic case of the Bethe scattering theory. The cross sections for N2, O2, and CO2 molecular targets were obtained using the additivity rule. The results presented are compared with known experimental and theoretical data.  相似文献   

18.
Ne原子与H2分子碰撞的同位素替代效应研究   总被引:1,自引:0,他引:1       下载免费PDF全文
使用密耦近似(Close-Coupling)方法、采用Tang-Toennies势模型计算了惰性气体原子Ne与H2分子及同位素D2分子在碰撞能量为83.8 meV时的微分散射截面及分波截面, 并与实验值和文献值进行比较.计算得到的微分散射截面值与实验值符合得较好,分波截面值与文献值也相符合.使用同样的方法和模型,文中对Ne-H2(D2,T2)三个体系的微分截面和分波截面进行了系统计算和比较分析,得出对称同位素替代碰撞体系的散射截面规律. 关键词: 2(D2')" href="#">Ne-H2(D2 2)碰撞')" href="#">T2)碰撞 Tang-Toennies势模型 密耦方法 同位素替代  相似文献   

19.
Explicit forms for the two-photon absorption cross section in linearly and circularly polarized light for rotating diatomic molecules have been developed. The ratio (σλλ/σ cc ) of the cross sections for individual rotational transitions is precisely two-thirds for all branches of ΔΩ = 0, ±1, ±2 transitions except for the unique case—the Q branch of a ΔΩ=0 transition. In the latter case the ratio becomes J-dependent and may range from infinity to 4/1 (for high J) for different relative contributions to the absorption cross section of intermediate states having either the same or different electronic symmetry. These contributions are thus experimentally accessible in this favourable situation.  相似文献   

20.
The cross sections for the collision induced transfer2P1/2mj=1/2 → mj = ?1/2 optically polarized Rb-vapour has been measured for collisions with He, Kr and Xe in the temperature range 30 °C → ~ 400 °C. The measurements were done by observing the degree of polarization in the fluorescent light emitted by the Rb-vapour. To avoid hyperfine structure effects, the nuclear spin was decoupled with a magnetic field. Calculations are presented in the temperature range 20 K → 1000 K using a semiclassical treatment and the Pascale Vandeplanque potentials. In the case of helium theoretical and experimental results are at variance, whereas for krypton and xenon satisfactory agreement is obtained. For the heavy rare gases the importance of trajectory effects, notably orbiting, becomes apparent.  相似文献   

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