Population coherent control of a Rydberg sodium atom in a microwave field

The B-spline expansion technique and the time-dependent multilevel approach (TDMA) are used to study the interaction between a microwave field and sodium atoms. The Rydberg sodium atom energy levels of p states in zero field are calculated, and the results are in good agreement with the other theoretical ones. The time evolutions during the population transfers of the five states from n = 75 to n = 79 in different microwave fields are obtained. The results show that the coherent control of the population transfer from the lower states to the higher ones can be accomplished by optimizing the microwave pulse parameters.     

Population coherent control of Rydberg potassium atom via adiabatic passage

The time-dependent multilevel approach(TDMA) and B-spline expansion technique are used to study the coherent population transfer between the quantum states of a potassium atom by a single frequency-chirped microwave pulse.The Rydberg potassium atom energy levels of n=6-15,l=0-5 states in zero field are calculated and the results are in good agreement with other theoretical values.The time evolutions of the population transfer of the six states from n=70 to n=75 in different microwave fields are obtained.The results show that the coherent control of the population transfer from the lower states to the higher ones can be accomplished by optimizing the microwave pulse parameters.     

啁啾微波场中里德伯钠原子高激发态的布居跃迁

采用含时多态展开方法, 结合B样条函数和单电子原子模型势研究微波场中钠原子里德伯高激发态的性质, 得到钠原子的能级结构及在微波场中的布居数迁移, 实现对量子态的操纵与控制. 结果表明: 含时多态展开方法结合B样条函数和单电子原子模型势是有效研究微波场中碱金属原子性质的一种方法; 选择合适的啁啾率、振幅等参数, 可以实现布居数在量子态之间的完全迁移和量子态囚禁.     

Laser pulse design for coherent control of Rydberg lithium atoms

<正>Using the time-dependent multilevel approach(TDML),this paper studies the dynamics of coherent control of Rydberg lithium atoms and demonstrates that Rydberg lithium atoms can be transferred to states of higher principal quantum number by exposing them to specially designed frequency-chirped laser pulses.The population transfer from n= 70 to n= 75 states of lithium atoms with efficiency of more than 90%is achieved by means of the sequential adiabatic rapid passages.The results agree well with the experimental ones and show that the coherent control of the population transfer from the lower n to the higher n states can be accomplished by the optimization of the chirping parameters and the intensity of laser field.     

Effect of electron correlation on high-order harmonic generation in helium model atom

High-order harmonic generation (HHG) of a helium model atom in an intense laser field has been numerically investigated. The influence of electron correlation on HHG is analysed by changing the strength between the electrons. The numerical results show that as the electron interaction strength becomes small, the first ionization energy increases rapidly, which results in the decrease in ionization. So the conversion efficiency of the high harmonic lying in the plateau decreases greatly, while the cutoff harmonic order in the harmonic spectrum increases.     

啁啾微波场中里德伯锂原子的相干激发与控制

运用含时多态展开方法和B-样条函数研究了微波场中里德伯锂原子高激发态的性质,得到锂原子量子态n=70-75,l=0-5的能量,并分析了里德伯锂原子高激发态n=70-75,l=0-5在微波场中的跃迁几率.结果表明:通过优化微波场参数可以实现量子系统从初始态到目标态的完全跃迁,且在跃迁过程中,每个l态都起至关重要的作用.     

Study of frequency-modulated excitation of Rydberg potassium atoms by using B-spline

With the B-spline expansion technique and a model potential of the alkali atoms, the properties of frequency-modulated excitation of Rydberg potassium atoms in a static electric field and a microwave field are investigated by using the time-dependent two-level approach. We successfully reproduce the square wave oscillations in the low frequency, the stair step population oscillations in the intermediate frequency, and the multiphoton transitions in the high frequency with respect to the unmodulated Rabi frequency, which have been observed experimentally by Noel et al. [Phys. Rev. A 58 2265 (1998)]. Furthermore, we also numerically obtain the discretized Rabi oscillations predicted in the Landau-Zener accumulation model.     

Population transfer via adiabatic passage in the Rydberg potassium atom

Using the time-dependent multilevel approach, we have calculated the coherent population transfer between the quantum states of potassium atom by a single frequency-chirped laser pulse. The result shows that a pair of sequential `broadband' frequency-chirped laser pulses can efficiently transfer population from the initial state of the ladder system to the target state. It is also found that the population can be efficiently transferred to a target state and trapped there by using an `intuitive' or a `counterintuitive' frequency sweep laser pulse in the case of `narrowband' frequency-chirped laser pulse. Our research shows that the complete population transfer is related to the pulse duration, chirp rate, and amplitude of the laser pulse.     

微波场中里德堡锂原子的高激发跃迁

运用含时多态展开方法研究微波场中里德堡锂原子高激发态的性质,得到锂原子在微波场中的跃迁几率,实现对量子态的操纵与控制。结果表明：选择合适的振幅、频率等参数,可以实现布居数在量子态之间的完全跃迁。     

里德伯钠原子经绝热快速通道的布居数跃迁相干控制

运用含时多态展开方法和B-样条函数研究了啁啾频率微波场中里德伯钠原子的量子态之间的布居数迁移.计算了里德伯钠原子n=70-77的开普勒频率.计算了在不同的微波场中六个态的布居数从n=70到n=77随时间的迁移,布居数跃迁到最终态n=77达到了98%,这可以通过连续的单光子跃迁来实现.结果表明,通过优化微波脉冲参数可以实现从低态到较高态的布居跃迁的相干控制.     

Dynamics of a three-level V-type atom driven by a cavity photon and microwave field

We discuss the dynamics of a three-level V-type atom driven simultaneously by a cavity photon and microwave field by examining the atomic population evolution. Owing to the coupling effect of the cavity photon, periodical oscillation of the population between the two upper states and the ground state takes place, which is the well-known vacuum Rabi oscillation. Meanwhile, the population exchange between the upmost level and the middle level can occur due to the driving action of the external microwave field. The general dynamic behavior is the superposition of a fast and a slow periodical oscillation under the cooperative and competitive effect of the cavity photon and the microwave field. Numerical results demonstrate that the time evolution of the population is strongly dependent on the atom–cavity coupling coefficient g and Rabi frequency ?_e that reflects the intensity of the external microwave field. By modulating the two parameters g and ?_e, a large number of population transfer behaviors can be achieved.     

Coherent population transfer in Rydberg potassium atom by a single frequency-chirped laser pulse

By using the time-dependent multilevel approach, we have calculated the coherent population transfer among the quantum states of potassium atom by a single frequency-chirped laser pulse. The results show that the population can be efficiently transferred to a target state and be trapped there by using an `intuitive' or a `counter-intuitive' frequency sweep laser pulse in the case of `narrowband' frequency-chirped laser pulse. It is also found that a pair of sequential `broadband' frequency-chirped laser pulses can efficiently transfer population from one ground state of the \La atom to the other one.     

高斯型微波脉冲强度和半宽对里德堡钾原子相干跃迁布居的影响

利用含时多态展开方法(the time-dependent multilevel approach, TDML）,计算了脉冲强度及半宽对里德堡钾原子相干跃迁布居数的影响。结果表明,脉冲强度的单纯增加并不能在本质上提高目标态布居数的迁移率。 在脉冲强度及半宽双因素共同作用下,单色激光驱动里德堡钾原子相干激发时,目标态的跃迁几率仅取决于脉冲的强度和半宽乘积。     

高斯型微波脉冲强度和半宽对里德堡钾原子相干跃迁布居的影响

利用含时多态展开方法(the time-dependent multilevel approach, TDML）,计算了脉冲强度及半宽对里德堡钾原子相干跃迁布居数的影响。结果表明,脉冲强度的单纯增加并不能在本质上提高目标态布居数的迁移率。 在脉冲强度及半宽双因素共同作用下,单色激光驱动里德堡钾原子相干激发时,目标态的跃迁几率仅取决于脉冲的强度和半宽乘积。     

Population transfer of sodium in a single analytical laser pulse

The population transfer of sodium in a single analytical laser pulse was studied in three models:two-level sodium,three-level sodium and many-level sodium.The effect of a third state on a two-level system was studied by investigating a ladder three-level system.Two effects were found in the vicinity of the resonance frequency.     

Laser pulse design for coherent laser control of potassium atoms

In this paper, the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach (TDMA). The calculation results of population transfer are presented with different laser fields. The results show that the population can be transferred to target state completely by a specially designed laser field.     

锂原子的高激发态能级计算及其在微波场中的布居动力学过程

利用B样条技术,设计了一种计算高激发原子能级结构的方法,计算了高激发锂原子的能级结构,并研究了里德堡锂原子在微波场中的布居动力学过程。     

里德堡钾原子的布居数在受激拉曼绝热通道中的相干迁移

本文用含时多态展开方法研究了在两束部分重叠的脉冲场驱动下布居数在钾原子量子态中的相干迁移。结果表明，布居数能否实现完全迁移取决于两个脉冲的持续时间和重叠程度，当脉冲的持续时间和重叠合适时，将发生布居数的完全迁移，并形成布居数囚禁。     

BeC，BeC2分子的结构与势能函数

应用密度泛函B3P86/aug-cc-pvtz方法对BeC(X )进行了理论计算,得到BeC分子基态的平衡核间距为0.1666 nm,离解能为2.3185eV,与其它理论结果符合得非常好,并进一步计算了谐振频率为917.9114 cm-1,得到该分子的Murrell-Sorbie势能函数。用QCISD/6-311++G（3df,3pd）方法优化出BeC2(X1A1)分子的稳定构型为C2V,其平衡核间距 =0.1615 nm、 ,并计算了离解能、力常数及谐振频率。在推导BeC2的离解极限基础上,应用多体展式理论方法,推导出基态BeC2分子的解析势能函数,该势能面准确呈现出BeC2`(X1A1)分子基态的结构特征和能量变化。     

BeC，BeC2分子的结构与势能函数

应用密度泛函B3P86/aug-cc-pvtz方法对BeC(X )进行了理论计算,得到BeC分子基态的平衡核间距为0.1666 nm,离解能为2.3185eV,与其它理论结果符合得非常好,并进一步计算了谐振频率为917.9114 cm-1,得到该分子的Murrell-Sorbie势能函数。用QCISD/6-311++G（3df,3pd）方法优化出BeC2(X1A1)分子的稳定构型为C2V,其平衡核间距 =0.1615 nm、 ,并计算了离解能、力常数及谐振频率。在推导BeC2的离解极限基础上,应用多体展式理论方法,推导出基态BeC2分子的解析势能函数,该势能面准确呈现出BeC2`(X1A1)分子基态的结构特征和能量变化。