激发光线宽对原子光致漂移速率的影响

在光致漂移效应的研究中,激发光线宽会改变原子激发的速度选择性,进而影响漂移速率的大小.本文以原子光致漂移速率方程理论为基础,利用强碰撞模型描述原子与缓冲气体的碰撞作用,运用数值方法对速率方程进行求解计算,研究了激发光线宽对原子漂移速率的影响.研究结果表明,其他条件相同时,随着线宽的增大,漂移速率的值呈现先增大后减小的趋势.存在一个最佳的激发光线宽,使得原子的漂移速率达到最大值.最佳线宽与激发光功率密度、温度和缓冲气体压强有关.为了获得最佳的光致漂移效果,激发光应工作在最佳线宽条件下.当激发光线宽在最佳线宽附近波动时,设置激发光线宽略大于最佳线宽可减少线宽波动对漂移速率的影响,对获得较大漂移速率更为有利.     

Light-induced drift of ions in a magnetic field

The effect of a magnetic field on the ion drift in a weakly ionized gas under the combined action of the light-induced drift and light pressure is studied theoretically. It is shown that, under the action of light, a component of ion drift velocity transverse to the direction of propagation of radiation may appear in a weakly ionized gas upon the application of an external magnetic field. It is shown that the Lorentz force acting on ions in the magnetic field radically changes the dependence of the ion drift velocity on the radiation frequency detuning. It is predicted that the ion drift velocity component along the direction of radiation must reverse its sign upon an increase in the magnetic field and an anomalous light-induced drift may be observed.     

Influence of a strong magnetic field on the hydrogen molecular ion using B-spline-type basis-sets

As an improvement on our previous work [J. Phys. B: At. Mol. Opt. Phys. 45 085101(2012)], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low excited states1σu, 1πg,u, 1δg,u, 2σg of the H+2in magnetic fields ranging from 109Gs(1 Gs = 10-4T) to 4.414 × 1013 Gs. Comparing the one-center method used in our previous work, the present method has a higher precision with a shorter computing time.Equilibrium distances of the states of the H+2in strong magnetic fields were found to be accurate to 3~5 significant digits(s.d.) and the total energies 6~11 s.d., even for some antibonding state, such as 1πg, which is difficult for the one-center method to give reliable results while the field strength is B ≥ 1013 Gs. For the large disagreement in previous works, such as the equilibrium distances of the 1πg state at B = 109 Gs, the present data may be used as a reference. Further, the potential energy curves(PECs) and the electronic probability density distributions(EPDDs) of the bound states 1σg, 1πu, 1δg and antibonding states 1σu, 1πg, 1δu for B = 1, 10, 100, 1000 a.u.(atomic unit) are compared, so that the different influences of the magnetic fields on the chemical bonds of the bound states and antibonding states are discussed in detail.     

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讨论了静态非均匀磁场中的磁场旋度对带电粒子引导中心漂移的影响。运用三维矢量分析的方法,将带电粒子垂直于磁场运动所引起的磁场漂移分为两项,分别由磁场的曲率和磁场的旋度决定。给出了螺旋状环形磁场中由磁场旋度引起的磁场漂移的近似表达式,讨论了该漂移成分对于该磁场中通行粒子轨道和捕获粒子轨道的可能影响。结果表明,带电粒子垂直于磁场运动所引起的磁场漂移主要由磁场的曲率决定,而磁场旋度对该漂移的影响比较微弱。     

磁场旋度对磁场漂移的影响

讨论了静态非均匀磁场中的磁场旋度对带电粒子引导中心漂移的影响。运用三维矢量分析的方法,将带电粒子垂直于磁场运动所引起的磁场漂移分为两项,分别由磁场的曲率和磁场的旋度决定。给出了螺旋状环形磁场中由磁场旋度引起的磁场漂移的近似表达式,讨论了该漂移成分对于该磁场中通行粒子轨道和捕获粒子轨道的可能影响。结果表明,带电粒子垂直于磁场运动所引起的磁场漂移主要由磁场的曲率决定,而磁场旋度对该漂移的影响比较微弱。     

On the influence of a weak magnetic field on the drift motion of charged particles

The results obtained in [1] are generalized to the case when an arbitrarily oriented magnetic field is present by allowance for the influence of a magnetic field with cyclotron frequency less than the collision frequency on the dependence of the drift velocity on the velocity of random motion (Langevin equation). A study is made of the influence of a magnetic field on the equation of drift motion derived in [1] and this field is allowed for in the previously obtained results of the solution of that equation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 69–72, May, 1972.     

Anomalous light-induced drift of linear molecules

The sudden approximation in energy is used to derive analytic formulas that describe the anomalous light-induced drift (LID) of linear molecules absorbing radiation in the rovibrational transition nJ _i −mJ _f (n and m are the ground and excited vibrational states, and J _α is the rotational quantum number in the vibrational state α=m, n). It is shown that for all linear molecules with moderate values B≲1 cm⁻¹ of the rotational constant, anomalous LID can always by observed under the proper experimental conditions; temperature T, rotational quantum number J _i , and type of transition (P or R). The parameter γ=B[J _i (J _i +1)−J _f (J _f +1)] ν _n /2k _BT (ν _m −ν _n ) is used to derive a condition for observing anomalous LID: γ∼1 (k _B is the Boltzmann constant and ν _α is the transport rate of collisions of molecules in the vibrational state α and buffer particles at moderate molecular velocities , where is the most probable velocity of the buffer particles). For ν _m >ν _n anomalous LID can be observed only in P-transitions, while for ν _m <ν _n it can be observed only in R-transitions. It is shown that anomalous LID is possible for all ratios β=M _b /M of the masses of the buffer particles (M _b ) and of the resonant particles (M) and any absorption-line broadening (Doppler or homogeneous). The optimum conditions for observing anomalous LID are realized when the absorption line is Doppler-broadened in an atmosphere of medium-weight (β∼1) and heavy (β≫1) buffer particles. In this case, anomalous LID can be observed in the same transition within a broad temperature interval ΔT∼T. If the buffer particles are light (β≪1) or if the broadening of the absorption line is homogeneous, anomalous LID in the same transition can be observed only within a narrow temperature range ΔT≪T. Zh. éksp. Teor. Fiz. 115, 1664–1679 (May 1999)     

Two-dimensional hydrogen negative ion in a magnetic field

Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H^{-} in a magnetic field. The results show that the ground and low-excited states of H^{-} in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.     

Influence of the lower-hybrid drift instability on magnetic reconnection in asymmetric configurations

Using fully kinetic 3D simulations of magnetic reconnection in asymmetric antiparallel configurations, we demonstrate that an electromagnetic lower-hybrid drift instability (LHDI) localized near the X line can substantially modify the reconnection mechanism in the regimes with large asymmetry, a moderate ratio of electron to ion temperature, and low plasma β. However, the mode saturates at a small amplitude in the regimes typical of Earth's magnetopause. In these cases, LHDI-driven turbulence is predominantly localized along the separatrices on the low-β side of the current sheet, in agreement with spacecraft observations.     

Theory of light-induced drift of a binary gas mixture in a capillary

The drift of a binary gas mixture in capillaries induced by resonant light is studied theoretically. The surface and bulk mechanisms of flow of the mixture components are analyzed for arbitrary values of the Knudsen number and the rate parameter (the ratio of the radiative decay rate of an excited molecular level to the intermolecular collision rate). Finally, the theoretical results are compared with the experimental data. Zh. éksp. Teor. Fiz. 114, 1709–1722 (November 1998)     

强流磁约束金属离子注入源

设计和制造了适合工业应用的强流金属离子源。离子源的电弧阴、阳电极之间和放电室壁采用永磁体阵列形成导流、屏蔽磁场,改进了电弧的放电特性和提高等离子体密度。离子注入源在加速电压为30kV、50 Hz 条件时,平均束流流强约为30mA,调试结果表明附加磁场提高了离子源性能。     

Concentration of lithium vapor in a high-temperature sapphire capillary based on light-induced drift

The accumulation of atomic lithium vapor in a sapphire capillary based on light-induced drift is experimentally investigated. To suppress lithium adsorption on the walls of the capillary and prolong the life of the atomic state, the capillary was heated to high temperatures. The phenomenon of an “optical piston” was observed, indicating a high degree of concentration of atomic lithium vapor. The experimental results are consistent with theoretical ideas, and they suggest that heated cells hold some promise for efficient isotope separation and the detection of atomic micro-impurities. Zh. éksp. Teor. Fiz. 114, 1162–1170 (October 1998)     

扫场对核磁共振测量的影响

在连续波核磁共振实验中，通常采用低频扫场产生重复再现的共振吸收信号。当处于磁场中的射频线圈引线回路等效面积不为零时，简谐扫场必然引起该闭合回路的磁通量变化，由此而产生同频简谐感生电动势并与核磁共振信号叠加共同构成振荡器输出信号。由于扫场上升和下降过程的感生电动势方向相反，从而扫场前半周和后半周所对应的共振吸收测量信号存在差异。实验结果表明：扫场强度及方向对核磁共振测量影响来源于实验测量技术缺陷，而非核磁共振的物理本质。     

Influence of a constant magnetic field on the radiation of a planar undulator

The influence of a constant magnetic field on the radiation of a planar undulator is studied analytically with the use of generalized Bessel functions. The behavior of on-axis radiation intensity in the undulator and the influence of a magnetic field on off-axis radiation are investigated. The critical magnitude of the constant component of the magnetic field, which has a significant effect on the motion of electrons in the undulator, is calculated analytically. The examples of several planar undulators are discussed, and the influence of the Earth’s magnetic field on their spectrum is evaluated.     

Characteristics of a hot ion collector placed in a weak ion cyclotron resonance magnetic field

The separation characteristics of a planar collector system placed in the weak magnetic field region of a facility that separates isotopes of stable metals by the ion-cyclotron-resonance method are calculated. An increase in the gyroradius of the accelerated ions in the weak field allows the designer to increase the collector plate spacing and decrease undesired screen losses. It is theoretically shown that placing the collector in the week field increases the degree of separation. Also, the transverse-to-longitudinal ion energy conversion makes it possible to extend the product deposition area on the collector plates and, thus, to reduce the thermal load on the collector and facilitate the long-term production of the target material in large amounts.     

Conservation law for the binormal momentum in the presence of charge drift in a magnetic field

It is well-known that the motion of a charged particle in a magnetic field is described by the drift approximation, in which it is assumed that the squared velocity of the particle and the magnetic moment of the Larmor circle are conserved. It is shown that to a first approximation a third conservation law is also satisfied: the unaveraged generalized momentum in the direction of the binormal to the reference flux line around which the particle rotates is conserved. This new conservation law makes it possible to determine additional fine details of the motion, specifically, the deflection of a particle in the direction of the normal to the reference flux line, in terms of which the known drift velocity along the binormal is expressed after averaging.