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1.
The B-spline expansion technique and the time-dependent multilevel approach (TDMA) are used to study the interaction between 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. 相似文献
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Using a time-dependent multilevel approach, we demonstrate
that lithium atoms can be transferred to states of lower principle
quantum number by exposing them to a frequency chirped microwave
pulse. The population transfer from n = 79 to n = 70 states of
lithium atoms with more than 80% efficiency is achieved by means
of the sequential two-photon Δ n = - 1 transitions. It is
shown that the coherent control of the population transfer can be
accomplished by the optimization of the chirping parameters and
microwave field strength. The calculation results agree well with
the experimental ones and novel explanations have been given to
understand the experimental results. 相似文献
4.
<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. 相似文献
5.
Coherent population transfer in Rydberg potassium atom by a single frequency-chirped laser pulse 下载免费PDF全文
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. 相似文献
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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. 相似文献
8.
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. 相似文献
9.
研究了少周期脉冲串作用下三能级原子中的布居转移和相干布居捕获现象.在非旋波近似的情况下求解了密度矩阵方程.研究结果表明在等时间间隔的锁相脉冲作用下,系统能级的布居逐步转移并积累,系统基态相干也逐步积累.在满足脉冲重复频率为基态能级频差的整数分之一倍时,三能级系统和频率梳中两梳齿频率成分作用形成相干布居捕获现象,原子暗态布居值达到最大,介质对脉冲透明.在适当选取少周期脉冲参量的情况下,在0.5个ns的时间内三能级系统相干性演化到最大后到达稳态,相干布居捕获发生.与脉宽为100个fs的多周期脉冲相比,少周期脉冲串在介质中建立相干布居捕获的时间缩短两个数量级.由于频率梳中与三能级系统发生作用的梳频成份有相同的频移,相干布居捕获的条件双光子共振仍然满足.因而,当两基态能级频率差较大时,如果选取少周期脉冲载波频率为系统能级1至2和1至3的传输频率之和的一半ω=(ω1+ω2)/2,室温下原子热运动的引起的多普勒频移并不会破坏相干布居捕获. 相似文献
10.
Kerr效应对非线性Jaynes-Cummings模型场熵和缠结的影响 总被引:4,自引:2,他引:2
Phoenix和Knight提出的量子熵理论,用量子熵作为缠结程度的量度,研究了附加克尔介质依赖强度耦合Jaynes-Cummings模型场熵演化的动力学特性和原子-场的缠结特性,详细地讨论了克尔效应及初始相干光场的强弱对场熵演化特性和原子-场缠结特性的影响,并与原子反转特性相比较.结果表明:在初始相干光场较弱时(n=10),克尔介质的非线性相互作用破坏了场熵演化的周期性,原子-场不再周期消缠结.但在初始相干光场较强时(n=50),克尔介质非线性相互作用只是使场熵演化的周期性减弱,场熵的演化仍近似地有周期性,原子-场仍周期消缠结,克尔效应越强,周期越小.当克尔介质与光场强耦合相互作用时(χ/g=5),原子-场持续消缠结. 相似文献
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Within the Franck–Condon approximation, the single ionisation of H2 leaves H+2 in a coherent superposition of 19 nuclear vibrational states. We numerically design an optimal laser pulse train to transfer such a coherent nuclear wave packet to the ground vibrational state of H+2. Frequency analysis of the designed optimal pulse reveals that the transfer principle is mainly an anti-Stokes transition, i.e. the H+2 in 1sσg with excited nuclear vibrational states is first pumped to 2pσg state by the pulse at an appropriate time, and then dumped back to 1sσg with lower excited or ground vibrational states. The simulation results show that the population of the ground state after the transfer is more than 91%. To the best of our knowledge, this is the highest transition probability when the driving laser field is dozens of femtoseconds. 相似文献
13.
WnC0,± (n=1-6) clusters are investigated by using the density functional theory (DFT) at the B3LYP/LANL2DZ level. We find that the neutral, anionic and cationic ground state structures are similar within the same size, and constituted by substituting a C atom for one W atom in the structures of Wn+1 clusters. The natural bond orbital (NBO) charge analyses indicate that the direction of electron transfer is from the W atom to the 2p orbital of the C atom. In addition, the calculated infrared spectra of the WnC0,± (n=2-6) clusters manifest that the vibrational frequencies of neutral, anionic and cationic clusters are similar in a range of 80 cm-1-864 cm-1. The high frequency, strong peak modes are found to be an almost stretched deformation of the carbide atom. Finally, the polarizabilities of WnC0,± (n=1-6) clusters are also discussed. 相似文献
14.
Jing-Xin Cui Zi-Dan Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(9):1-6
The state transfer from cesium nS (n = 45?53) states to Stark (product) states induced by a weak electric field (WEF) pulse was investigated using the state-selective field ionization method in a standard magneto-optic trap (MOT). The WEF pulse shifts the nS Rydberg states that anticross with the (n ? 4) hydrogen-like manifolds, causing state transitions from the initial excited nS state to the Stark states. The mechanism of transfer was investigated by changing the rising and falling time of the WEF pulse and the switching off time of the external field pulse had an important role during the evolution process of product states. The population of the product states is also measured as a function of the principal quantum number and Rydberg densities. 相似文献
15.
利用光电子能谱及密度泛函理论计算对TiGen-(n=7~12)团簇的几何结构及电子特性等进行了系统研究. 对于TiGen-负离子及中性TiGen,在n=8时出现了钛原子半内嵌的船型结构;在n=9~11时,新增的锗原子加盖到这种船型结构上,逐步形成钛原子完全内嵌的结构. TiGe12- 团簇具有一种钛原子内嵌的变形六棱柱结构. 自然布居分析结果显示,对于n=8~12的TiGen-/0 团簇,随着内嵌结构的形成,有电子从锗原子转移到钛原子,说明其电荷转移方式与结构演变密切相关. 相似文献
16.
Mathematical modeling of the population dynamics is performed for states of a three-level system (atom) with a V-type configuration transforming a light pulse. It is assumed that the excited eigenstates of the atom are degenerate and coupled by coherent interaction, one of the states being radiating (radiative), while the other state is nonradiating (??dark??). The population dynamics of atomic states is described on the basis of numerical solutions of equations for the matrix elements of the density operator. The dependence of the efficiency of population of the atomic dark state from the values of the parameters of an irradiation pulse and from the ratio of the period of population oscillations of excited atomic states (caused by their coherent interaction) to the lifetime of the atomic radiating state is determined. Typical examples of the time dependence of the population of states of the atom considered are presented for the cases of irradiation by a short (as compared to the lifetime of the radiating state) sinusoidal light pulse and by a long rectangular light pulse with the resonance carrier frequency. 相似文献
17.
A. Wetzels A. Gürtler H.G. Muller L.D. Noordam 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):157-165
An optically excited Rydberg wavepacket can be generated by exciting the electron from a low-lying state to a coherent superposition
of high-lying states with a short broadband optical pulse. A special kind of Rydberg wavepacket is generated in the case of
a interaction of a weak THz half cycle pulse with a stationary Rydberg state, called the THz wavepacket. This THz wavepacket
is a coherent superposition of the initial Rydberg state and its neighbouring states. We have investigated the time evolution
of THz wavepackets by measuring the impact of two in time delayed half cycle pulses ( ≈ 200 V cm-1) on the population of a stationary (n = 40) Rydberg state in rubidium. The first half cycle pulse creates the THz wavepacket and the second half cycle pulse probes
the dynamics of the THz wavepacket. We support our experimental data by numerically solving the Schr?dinger equation and with
a semi-classical picture. Whereas an optically excited wavepacket is initially localized, a THz wavepacket is initially delocalized
and becomes localized after half a revival time.
Received 23 August 2000 and Received in final form 27 March 2001 相似文献
18.
K. Ohshimo H. Tsunoyama F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):107-110
Intracluster electron transfer and oligomerization reaction were investigated by mass spectrometry of clusters of alkali metal
atom (M) with acrylonitrile (AN; CH2=CHCN). In the photoionization mass spectra of M(AN)n, magic numbers were clearly observed at n = 3k (k = 1-4 for M = Na and K, k = 1 for M = Li). The results of photodissociation of neutral K(AN)n indicate that the n = 3 cluster has an anomalous stability relative to other sizes of clusters. The C=C bond in vinyl molecules is also found
to be necessary to form the magic numbers by measuring the photoionization mass spectrum of K atom with propionitrile. These
results strongly support the intracluster anionic oligomerization reaction initiated by electron transfer from the alkali
atom. The quantum chemical calculations have revealed that the evaporation induced by excess energy generated by intracluster
oligomerization is important to form the magic numbers in the present clusters.
Received 29 November 2000 相似文献
19.
频率啁啾激光场中锂原子的激发与态囚禁 总被引:1,自引:1,他引:0
采用含时多态展开方法,对不同频率啁啾激光场中里德堡锂原子布居数的相干迁移特性进行了计算研究。结果表明:布居数跃迁几率对激光脉冲形状、激光场强度、啁啾率等参数非常敏感,在合适的激光参数下,可以实现布居数在四个量子态之间的完全迁移和量子态的囚禁。 相似文献