共查询到19条相似文献,搜索用时 156 毫秒
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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。 相似文献
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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. 相似文献
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本文研究了由体系的基态和较高激发态迭加形成的原子在强激光场作用下的高次谐波发射.观察电离波包的演化过程,阐明了谐波发射效率提高的原因.在给定入射激光条件下,通过选择不同的激发态,可以实现对谐波发射的控制. 相似文献
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通过数值求解激光驱动下电子在一维周期势场中运动的薛定谔方程,研究了晶体在激光场中发射的低阶谐波强度随激光波长的变化规律,结果表明,晶体发射低阶谐波强度随激光波长的变化规律与晶体发射高次谐波第一平台区域的变化规律不同.已有的研究表明晶体发射高次谐波第一平台区域的强度会随激光波长的增加而衰减,而我们发现晶体发射低阶谐波的强度会随激光波长的增加而增加.通过对晶体发射低阶谐波的时频分析、晶体价带能量变化与激光光子能量的关系,解释了晶体发射低阶谐波强度随激光波长增加而增加的原因. 相似文献
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在量子散射框架下,对真实激光场引进多光子相互作用准静态过程模型,考虑束缚-自由跃迁中电磁场的规范一致性及电子与激光场长程相互作用的极限,研究激光场对量子散射过程中三重微分散射截面的影响.多数共面非对称情况下激光场对三重微分散射截面有提升作用,此外靶原子处于激发态时binary峰出现分裂,激光场对三重微分散射截面也有放大作用. 相似文献
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在量子散射框架下,对真实激光场引进多光子相互作用准静态过程模型,考虑束缚-自由跃迁中电磁场的规范一致性及电子与激光场长程相互作用的极限,研究激光场对量子散射过程中三重微分散射截面的影响。多数共面非对称情况下激光场对三重微分散射截面有提升作用,此外靶原子处于激发态时binary峰出现分裂,激光场对三重微分散射截面也有放大作用。 相似文献
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本文从理论上研究了在双色频率梳激光场驱动下多光子谐波辐射光谱中的相位突变现象。我们利用Floquet理论非微扰地模拟了频率梳激光场与原子分子等量子系统的相互作用过程。谐波辐射信号是多光子偶极跃迁相干叠加的结果,通过调节频率梳激光场间的相对相位,可以相干地控制谐波辐射信号的强度。通过对谐波信号进行傅里叶变换,可以提取不同跃迁路径的相对相位信息。我们通过改变频率梳组激光场的强度和频率组分实现多光子跃迁频率,让其跨越共振跃迁频率时,谐波相位会发生突变。从而可以观测超强激光场驱动下量子系统共振跃迁频率的斯塔克能移。 相似文献
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B. Jana A. Majumder P. T. Kathar A. K. Das V. K. Mago 《Applied physics. B, Lasers and optics》2011,102(4):841-849
The kinetics of a two-step photoionization process in optically thick atomic medium of barium (Ba) is studied using the rate equation approach. In the first step, Ba atoms get resonantly excited by laser radiation from their ground state to an intermediate excited state and subsequently are ionized in the second step by another laser radiation. The absorption of exciting radiation is taken into account along its propagation direction (optically thick). However, the medium is assumed to be optically thin for the ionizing radiation. A numerical simulation is done to estimate the ionization yield for time-varying Gaussian shaped laser pulses. The required energy density of the laser pulse to saturate the excitation transition throughout the thick medium is calculated. The effect of optical delay between the laser beams on the ionization yield is simulated. The calculated ionization yield from the simulation is compared with the measured values. 相似文献
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B. A. Zon 《Journal of Experimental and Theoretical Physics》2000,91(5):899-904
A general formula is obtained for the probability of tunneling ionization of an atom accompanied by excitation of the core. This formula is a generalization of the Carlson formula for the probability of a single-photon two-electron transition in atoms. The limiting case of this formula, just as that of the Carlson formula, is the well-known random-perturbations approximation. Numerical results are presented for Zn, Sr, and Cd atoms. For these atoms the contribution of the excited states of singly charged ions to the probability of the formation of doubly charged ions is a nonmonotonic function of the laser radiation intensity. Analysis of the tunneling ionization of molecules shows that with overwhelming probability an ion is formed in the ground vibrational state, while for the standard photoionization the distribution over vibrational states is determined by the Franck-Condon factors. 相似文献
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The ionization of a model two-electron atom in the field of a strong ultrashort laser pulse is studied by numerical integration of the nonstationary Schrödinger equation describing the dynamics of a quantum system in the field of an electromagnetic wave. Pecularities of the two-electron ionization are analyzed for pulses whose duration amounts to one to two periods of oscillation of the electric field of the wave at different frequencies of the incident radiation. For extremely short pulses, the double ionization is found to be suppressed. This effect is caused by the finiteness of the interelectron energy exchange time during the laser action. Peculiarities of the generation of high-order harmonics and single XUV attosecond pulses upon ionization of atoms by laser pulses, whose duration is within one to two optical cycles, are investigated. 相似文献
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E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1998,86(2):328-334
The ionization of excited hydrogen-like atoms in a femtosecond laser pulse is studied by direct numerical integration of the time-dependent Schrödinger equation for a quantum system in the field of an electromagnetic wave. Expressions are obtained for the ionization probability of the system as a function of the parameters of the laser pulse and the initial state of the atom. Ionization suppression is found, confirming the basic premises of the theory of interference stabilization of Rydberg atoms. 相似文献
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在铯原子室温蒸气池中研究了弱射频场中Rydberg原子阶梯型三能级系统的电磁感应透明(EIT)效应.铯原子基态6S_(1/2)、第一激发态6P_(3/2)和Rydberg 48D_(5/2)态形成阶梯型三能级系统,探测光共振作用于6S_(1/2)(F=4)→6P_(3/2)(F′=5)的跃迁,耦合光在Rydberg跃迁线6P_(3/2)(F′=5)→48D_(5/2)附近扫描,形成Rydberg原子EIT.当对铯原子施加一个80 MHz的弱射频电场时,48D_(5/2)Rydberg原子的EIT光谱发生Stark频移和分裂,同时产生由射频场调制Rydberg能级的偶数级边带,测量结果与Floquet理论模拟的结果相符合.同时,改变弱射频电场的频率研究了铯Rydberg能级的自电离效应对Rydberg原子Stark谱的影响,据此,我们提出将电极板置于铯原子蒸气池内的方案以减少自电离效应的影响.在弱射频Stark谱中,mj=5/2的Stark谱与mj=1/2,3/2的二级边带形成多个能级交叉,这些能级交叉点提供了一种基于原子的精确校准射频电场的新方法. 相似文献
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We show that it is possible to produce nearly bandwidth-limited few-cycle attosecond pulses based on periodic resonance interaction of a quasi-monochromatic radiation with the bound states of hydrogenlike atoms. A periodic resonance is provided by a far-off-resonant laser field with intensity much below the atomic ionization threshold via periodic tunnel ionization from the excited states and adiabatic Stark splitting of the excited energy levels. Without external synchronization of the spectral components, it is possible to produce 135 as pulses at 13.5 nm in Li2?-plasma controlled by radiation of a mode-locked Nd:YAG laser, as well as 1.25 fs pulses at 122 nm in atomic hydrogen controlled by radiation of a CO? laser. 相似文献
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The dynamics of hydrogen atom in the presence of a strong radiation field of the titanium-sapphire laser is studied for the Keldysh parameters γ ≥ 1 and γ ≤ 1. It is demonstrated that the ionization is supplemented with the effective population of the excited states with the principal quantum numbers n = 5–10 in the entire range of variation in the Keldysh parameter. The population of the excited Rydberg states can be interpreted as a consequence of the multiphoton resonance involving the initial 1s state and a group of excited states in the vicinity of the continuum boundary with the simultaneous repopulation of these states by Λ-type Raman transitions under the action of the laser field. The resulting coherent Rydberg packet appears to be stable with respect to ionization, so that the ionization of the atomic system in the presence of strong electromagnetic field is suppressed. Physical reasons for the stabilization are discussed. An interpretation of the effective population of the Rydberg states in the recent experiments on the ionization of atomic helium by the titanium-sapphire laser is proposed. 相似文献