桌面飞秒极紫外光原子超快动力学实验装置

飞秒极紫外光脉冲是研究原子分子超快动力学过程的重要工具,是同步辐射及自由电子激光这样的大科学装置的重要补充,而且具有非常诱人的发展前景.本工作基于大功率飞秒近红外激光在气体介质中的高次谐波过程,搭建了一套桌面飞秒极紫外光源.使用充气的中空波导管产生高次谐波,增大了驱动光与介质的作用长度,显著提高了光子产额.使用了光栅的圆锥衍射模式来实现高次谐波光子能量的选择,在保证高衍射效率的同时,减小了光栅衍射对于光脉冲的时间展宽效应.通过实际测量,光源的输出光子能量可覆盖20-90 eV的范围.在光子能量为40 eV附近,输出光子流强达1×10^10 photons/s,光子能量分辨约为0.4 eV.该光源结合新研制的反应显微成像谱仪,为研究极紫外光与原子分子的相互作用提供了独特的手段.目前已成功开展多次原子及分子电离实验,系统性能稳定.

4-2 Lifetime and the Ratio of 12C3+ and 16O4+ at the CSRe

Laser cooling is the most promising method to achieve high phase-space densities, even crystalline beams for relativistic heavy ion at storage rings[1]. A test laser cooling experiment has been performed with 12C3+ ions at the CSRe. In this experiment, the 12C3+ ions were produced from an electron cyclotron resonance (ECR) ion source, and due to the residual gas and the injection gases such as CO and CO2, 16O4+ ions will be produced at the same time.

4-9 Progress of Laser Cooling of 12C3+ Ions at the CSRe

Laser cooling is one of the most promising techniques to reach high phase-space densities and achieve phasetransition, ordered beam even crystalline beam for relativistic heavy ion beams at storage rings[1]. In order torealize laser cooling at the CSRe in IMP, we performed a test experiment by using a pulsed laser system to coolthe relativistic 12C3+ ion beams on the CSRe in September 2014. Fig. 1 is the schematic view of the experimentalsetup.

4-6 Measurement of the Ratio of C3+ and O4+ Ions Produced by ECR Source to Prepare a Laser Cooling Experiment at Storage Rings

The cooling of heavy ions can provide high-quality beams that are especially important for high-precisionexperimental nuclear and atomic physics. The laser cooling of relativistic C3+ ion beams at the experimental coolerstorage ring (CSRe) is being currently prepared at Institute of Modern Physics (IMP) in Lanzhou. An electroncyclotron resonance ion source (ECRIS) will be used to produce C3+ ion beams. Meanwhile, O4+ ions could alsobe produced due to residual gas because of the same mass-to-charge ratio. Therefore, both C3+ and O4+ ion beamswill be injected and circulate in a storage ring during the laser cooling experiment at the same time. A higher ratioof C3+ ions will lead to a better result for the laser cooling experiment.

4-8 Test Experiments of Laser Propagation and Control for Laser Cooling Experiment at the CSRe

Laser cooling of heavy ion beams is the most promising method to realize crystalline beams at storage rings[1].In order to perform the laser cooling experiment of C3+ at the CSRe[2], we tested the laser propagation and controlby using the He-Ne laser at the straight part (about 25 m long) before the experiment. The experimental resultsindicated that the laser was collimated and stable, and the laser intensity was strong enough after a long distancepropagation at the CSRe which satis ed the requirement of laser cooling of heavy ion beams.

Laser Cooling of Relativistic Li-like O^(5+) Ion Beams at Heavy-ion Storage Ring CSRe

Laser cooling is one of the most promising techniques to achieve high phase-space densities or even crystalline beams for relativistic heavy ion beams at storage rings[1].Based on the success of laser cooling of C^(3+) at the ESR[2,3],and the experience of test laser cooling experiments at the CSRe[4],laser cooling of lithium-like O^(5+) ion beams with an relativistic energy of 275.7 MeV/u was achieved for the first time at the heavy-ion storage ring CSRe in Lanzhou,China.In the experiment,a CW laser system with a wavelength of 220 nm was used to match the optical transition of 2s1=2-2p1=2 of O^(5+)ions.In order to cool the relativistic ion beams with only one counterpropagating CW laser,the ion beams were bunched by applying a sinusoidal voltage to the RF-buncher system.Fig.

Measurement of the Lifetime and the Proportion of C^(3+) Ions as a Preparation for Laser Cooling Experiments at the CSRe

Laser cooling is the most promising method to achieve high phase-space densities,even crystalline beams for relativistic heavy ion at storage rings[1].While a pure ion beam is usually desirable for laser cooling experiments to avoid spurious heating effects by any non-cooled ion species,we have found the C^(3+) ion beams produced by an Electron Cyclotron Resonance(ECR)ion source to be mixed with a significant fraction of O^(4+),because these two ions have almost the same mass-to-charge ratio and could not be separated by the analyzing magnets.Therefore,both ion species were injected into the CSRe and present during all experiments.

Fully Differential Study of Few-body Dynamics in Multi-electron Atomic Fragmentation Processes

Employing the reaction microscope,the experiment of He^(2+)collisions on Ar was performed[1].We have measured fully momentum analyzed Ar^(3+) recoil ions and two ejected electrons as well as He+projectiles in coincidence with each other.Fully differential cross sections(seeing Fig.1)for electron transfer from the target to the projectile accompanied by the ejection of two additional target electrons were extracted.This is the first measuring fully differential cross section on the fivebody process which supplies the most rigorous test for the relative theories[2].To a large extent the data can be reproduced by an independent electron model.

3-3 Preparation for Laser Cooling of Relativistic Li-like 16O5+Ion Beams at the CSRe

Laser cooling of relativistic heavy ion beams at storage rings is one of the most promising techniques to reach high phase-space densities and achieve a phase transition,an ordered beam,or even a crystalline beam.Compared with the established cooling schemes at storage rings,such as electron cooling and stochastic cooling,laser cooling rate is expected to be much higher and laser-cooled ion beams could reach ultra-low temperatures(~mK).The preparation of laser cooling of 280 MeV/u 16O^5+ion beams at the experimental cooler storage ring CSRe is in progress at the Institute of Modern Physics[1],Chinese Academy of Sciences.

3-1 Probing the Geometry of Ar2N2 Cluster by Heavy Ions Impact

The molecular complexes play an important role in planet’s atmosphere and chemical reactions of astrophysics.The investigation of geometry configurations for molecular complexes is an important subject both in experimental and theoretical aspects.As a prototype molecular system,the investigation of geometry configuration of van der Waals cluster Ar2N2 attracts considerable attention recently.The different equilibrium configurations of Ar2N2 cluster were reported by experiments as linear conformation[1;2]and theoretical calculations as linear or spatial X-shaped conformations[3-6].

3-5 Asymmetric Young's Double-slit Interference in Double Electron Capture by He^2+from CO

Various processes occurring in collisions of ions with molecules have been attracting much attention[1].Of particular interests in such collisions are interference effects caused by coherent scattering/interaction of the ion on more than one atomic center[2,3].The studies of ion-molecule collisions have been mainly restricted to homodiatomic molecule(see Ref.[3]and references therein).In the present work,we study double electron capture in collisions between 30,135 keV/u He^2+ions and CO molecules which are accompanied by breakup of CO^2+into C+and O^+fragments.

3-4 Single Electron Capture in 30 keV and 100 keV He^+-He Collisions

Using the reaction microscope technique,we have performed kinematically complete measurements for single capture in He+collisions with He at 30 and 100 keV[1].The state-selective and the angular-differential cross sections were extracted from the experimental data and compared with our theoretical calculations based on the dynamic-screening classical trajectory Monte Carlo method(dCTMC).The measured recoil-ion longitudinal momentum distributions are shown in Fig.1.

基于XUV激光脉冲和反应显微成像技术的原子分子光物理实验平台

基于高次谐波技术的超快激光系统可以通过控制脉冲时序实现对目标量子态的精准操控,反应显微成像谱仪实现了4π立体角内对量子少体碰撞过程的准确测量,两项先进系统的结合将极大拓展量子少体动力学研究的领域。目前,高次谐波的单频选择至关重要,同时反应显微成像谱仪的分辨率受真空度及冷靶分散度的影响较大。中国科学院近代物理研究所通过采用多级差分、钛真空靶室的设计,使得谱仪的真空度达到10^–11 mbar量级,有效降低了本底噪声的影响;升级改造传统超音速冷靶系统的靶束产生装置,实现了靶厚度的自由调控,大大提高了探测器记录事件的准确性;本实验平台结合高次谐波产生多阶XUV脉冲单能化技术,实现了单能XUV超快激光系统和反应显微成像谱仪成功结合,该系统可以产生能量范围在20~100 eV之间的XUV脉冲,能够研究电离能或解离能在100 eV以下的原子分子动力学过程。