铯原子nP_(3/2)(n=70—94)里德伯态的紫外单光子激发及量子亏损测量

基于成熟的光纤激光器、光纤放大器及高效激光频率转换技术,我们在实验中研制了一套瓦级输出的窄线宽连续波单频可调谐318.6 nm紫外激光系统,并在室温铯原子气室中实现了6S_(1/2)—nP_(3/2)(n=70—94)单光子跃迁里德伯激发.借助由铯原子6S_(1/2)(F=4)基态、6P_(3/2)(F′=5)激发态和nP_(3/2)(n=70—94)里德伯态构成的V型三能级系统,通过频率锁定于铯原子6S_(1/2)(F=4)—6P_(3/2)(F′=5)超精细跃迁的852.3 nm探测光束的吸收减弱信号获得了里德伯态的信息,并利用高精度波长计测量了铯原子nP_(3/2)(n=70—94)里德伯态的量子亏损值.经过与理论计算值的变化趋势进行对比,我们认为由于原子气室的里德伯屏蔽效应并不能完全屏蔽外部直流电场,铯原子气室内存在残余的直流电场,影响了对里德伯态的量子亏损值的实验测量.利用残余直流电场的Stark效应理论模型及其与有效主量子数n*的依赖关系,对铯原子里德伯态的量子亏损实验测量值进行了修正.修正后的铯原子nP_(3/2)(n=70—94)态量子亏损测量值为3.5591±0.0007,与理论计算值相吻合.     

超冷铯Rydberg原子寿命的测量

本文从实验上采用两步激发超冷基态原子获得超冷Rydberg原子,通过选择场电离的方法获得超冷Rydberg原子的离子信号.改变延迟时间测得Rydberg原子布居数随时间的变化关系,用两种方法拟合实验数据得到36D和34S态原子的有效寿命,与现有理论结果一致. 关键词： Rydberg原子 寿命 黑体辐射 场电离     

Cs 39D态Rydberg原子Stark光谱的实验研究

本文从理论和实验上对Cs39D态Rydberg原子在弱电场作用下的Stark效应做了详细研究. 理论上利用数值方法计算了Cs原子39D态的Stark结构;实验上,采用两步激发超冷基态原子获得超冷Rydberg原子,通过场电离的方法获得了39D态的Stark光谱,测量获得α^5/2₂,α^5/2₀,α^3/2₂和α^3/2₀相应的极化率分别为：62(7),－146(13), 73(6) 和－106(20) MHz·V^-2cm²,实验结果与理论相符合. 关键词： Rydberg原子 Stark结构 场电离 极化率     

Stark spectra of Rydberg states in atomic cesium in the vicinity of n=18

The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.     

Measuring the degree of unitarity for any quantum process

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.     

Measurement of quantum defect of nS and nD states using field ionization spectroscopy in ultracold cesium atoms

<正>This paper reports that ultracold atoms are populated into different nS and nD Rydberg states(n=25~52) by two-photon excitation.The ionization spectrum of an ultracold Rydberg atom is acquired in a cesium magneto-optical trap by using the method of pulse field ionization.This denotes nS and nD states in the ionization spectrum and fits the data of energy levels of different Rydberg states to obtain quantum defects of nS and nD states.     

Detection of frequency red shifts and blue shifts for single-mode IR laser radiation in Rydberg matter

Stimulated emission and laser gain were recently reported for the excited condensed matter Rydberg matter (RM). This shows that RM is in an excited and inverted state. A low-intensity single-mode IR laser beam is here red shifted in reflection from a layer of RM, and blue shifted when it passes through a cloud of RM. The shifts of approximately 0.02 cm^-1 are observed with a temperature-stable Fabry–Pérot interferometer. The process giving the wavelength shifts is proposed to be stimulated Raman scattering. RM is here formed from Rydberg states of both K atoms and nitrogen molecules inside a vacuum chamber, and it may be in liquid or solid form. PACS 78.30.-j; 42.65.Dr; 42.55.Ye     

弱射频场中Rydberg原子的电磁感应透明

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.     

QUANTUM DEFECT THEORY: RYDBERG STATES OF THE NO MOLECULES

The NO molecule.in Rydberg states consists of a closed shell molecular ion and an excited electron in a Rydberg molecular bital. It is a comparatively simple but non-trivial excited molecule. Here, we present our theoretical calculation of the quantum defects of these Rydberg states. The theoretical results are in good agreement with the experimental data.     

The dynamics of a THz Rydberg wavepacket

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     

铯47D精细能级超冷里德堡原子自由演化的动力学研究

用连续窄线宽激光器将超冷铯里德堡原子分别激发到47D_3/2, 47D_5/2精细态, 观察了处于里德堡精细态的铯原子向超冷铯等离子体自由演化的过程, 详细对比了不同精细态的铯里德堡原子预电离时间、电离速率以及等离子体的转化效率. 将里德堡原子快速转化为等离子体的过程解释为局域势阱内由预电离产生的电子与里德堡原子的快速碰撞导致的雪崩电离.     

Correlated photon emission from multiatom Rydberg dark States

We consider three-level atoms driven by two resonant light fields in a ladder scheme where the upper level is a highly excited Rydberg state. We show that the dipole-dipole interactions between Rydberg excited atoms prevents the formation of single particle dark states and leads to strongly correlated photon pairs from atoms separated by distances large compared to the emission wavelength. For a pair of atoms, this enables realization of an efficient photon-pair source with on average one pair every 30 μs.     

Properties of resonant interatomic Coulombic decay in Ne dimers

Properties of the interatomic Coulombic decay (ICD) process in Ne dimers have been obtained by tracking the formation of energetic Ne+ ions. The double photoionization cross section, deduced from the Ne+/Ne+ coincidence signal, is dominated by the ICD process and presents a threshold 280 meV below the atomic Ne+2s(-1) threshold. Rydberg excitation of a 2s electron in the dimer creates molecular Rydberg states whose Sigma and Pi symmetries have been resolved. These excited states decay by a resonant ICD process releasing an energetic Ne+ ion and a neutral excited Ne* fragment. Subsequent autoionization of the Ne* fragment explains a double photoionization threshold below the dimer 2s ionization threshold.     

Electric-field induced dipole blockade with Rydberg atoms

High resolution laser Stark excitation of np (60相似文献   

Rydberg quantum computation with nuclear spins in two-electron neutral atoms

Alkaline-earth-like (AEL) atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing. Typical AEL ground states possess no hyperfine splitting, but unfortunately a GHz-scale splitting seems necessary for Rydberg excitation. Though strong magnetic fields can induce a GHz-scale splitting, weak fields are desirable to avoid noise in experiments. Here, we provide two solutions to this outstanding challenge with realistic data of well-studied AEL isotopes. In the first theory, the two nuclear spin qubit states |0〉 and |1〉 are excited to Rydberg states |r〉 with detuning Δ and 0, respectively, where a MHz-scale detuning Δ arises from a weak magnetic field on the order of 1 G. With a proper ratio between Δ and Ω, the qubit state |1〉 can be fully excited to the Rydberg state while |0〉 remains there. In the second theory, we show that by choosing appropriate intermediate states a two-photon Rydberg excitation can proceed with only one nuclear spin qubit state. The second theory is applicable whatever the magnitude of the magnetic field is. These theories bring a versatile means for quantum computation by combining the broad applicability of Rydberg blockade and the incomparable advantages of nuclear-spin quantum memory in two-electron neutral atoms.     

Experimental study of highly excited even-parity bound states of the Sm atom

In this work, a three-step autoionization detection method and direct photoionization detection method are employed to measure the highly excited even-parity states of the Sm atom in the energy region between 36360~cm^-1 and 40800~cm^-1. Comparisons between the results from the two detection techniques enable us to discriminate the Rydberg states from the valence states in the same energy region with the information of level energies, possible J values and their relative intensities. Furthermore, in the experiment two different excitation schemes are designed to obtain the spectra of highly excited even-parity states of the Sm atom. With a detailed analysis of the experimental data, this work not only confirms the results about many spectral data from the literature with different excitation schemes, but also reports new spectral data on 29 Rydberg states and 23 valence states.     

铯原子里德伯态精细结构测量

里德伯态光谱是测量里德伯态能级结构和中性原子间相互作用的常用技术手段,特别是高精度的里德伯光谱,可以测量室温原子气室中由偶极相互作用等导致的原子能级频移.在实验中利用反向的852 nm激光和509 nm激光实现了室温原子气室中铯原子6S_(1/2)—6P_(3/2)—57S(D)跃迁的级联双光子激发,实现了里德伯态原子的制备.基于阶梯型电磁诱导透明获得了铯原子里德伯态的高分辨光谱.实验中,基于速度选择的射频边带调制技术,对光谱信号进行了频率标定,测量了铯原子里德伯态57D_(3/2)和57D_(5/2)的精细分裂,分裂间隔为(354.7±2.5)MHz,与理论计算结果基本一致.速度选择的射频调制光谱可以实现里德伯态原子的能级分裂测量,其测量精度对于单光子跃迁的绝对激光频率不敏感;实验中影响57D_(3/2)和57D_(5/2)精细分裂间隔测量精度的主要因素是功率加宽导致的电磁感应透明信号的展宽和509 nm激光频率扫描的非线性.     

The threshold electron impact spectrum of H2O

The threshold electron spectrum of H2 O was obtained using a high resolution electron impact spectrometer combined with the penetrating field method for scattered electrons with energies close to zero eV. The valence, triplet Rydberg states, as well as the resonances were identified and are discussed in the energy region 5.2–14.3 eV. The threshold spectrum confirms the influence of resonances on the enhancement of the intensity of some Rydberg states above 10 eV. The vibrational spacing of the observed transitions of the Rydberg states indicates that the water molecule is excited in the symmetric stretching mode.     

Chemical physics of the upper atmosphere

Modern concepts of the structure of the ionosphere and dynamics of its perturbations related to geomagnetic and solar activity perturbations are considered. It is shown that communication and navigation satellite systems depend substantially on the state of the ionosphere. The role played by Rydberg atoms and molecules of neutral ionospheric plasma components excited in collisions with electrons in the formation of microwave radiation of the upper atmosphere is discussed. A new physical mechanism of the delay of satellite signals cased by a cascade of reemissions from Rydberg states over the decimeter range is suggested.     

Eu原子4f~76snlRydberg态的研究

利用三步双色共振激发技术和三步三色孤立实激发技术,系统地研究了铕原子在42250—44510 cm~(-1)能域内的光谱特性,提供了该能域内56个束缚高激发态的光谱信息.为了能确定这些态的光谱归属,进行了两方面的探索:第一,观察能否利用孤立实激发技术,把处于这些态上的铕原子进一步共振激发到自电离态,从而推断这些态属于单电子激发的束缚Rydberg态还是属于双电子激发的价态,并对Rydberg态的电子组态进行了光谱确认;第二,通过计算这些态相对于各个电离阈的量子亏损并观察它们分别收敛于哪个电离阈,以便获取其主量子数的信息.最后,设计并采用了三种不同的激发路径,分别将原子布居到同一高激发能域并探测它们在该能域的光电离光谱.通过比较这些光谱的异同并结合上述激发路径所对应的跃迁选择定则,便可惟一地确定这些高激发态的总角动量.研究发现:所探测到的高激发束缚态只有三个属于单电子激发的束缚Rydberg态,其余都是价态.本文确定了这三个Rydberg态的电子组态和原子状态.