A study of the contribution of doubly excited ionic states to the properties of hot dense high-Z plasmas

The role of two-electron processes, i.e. dielectronic recombination and autoionization, in the ionization balance and X-ray emission of hot dense plasmas composed of various high-Z materials is explored. Tungsten, gold, lead and uranium are considered. It is shown that the average ion charge and the high-energy emissivity are both sensitive to the dielectronic recombination rate. A systematic study demonstrates the degree of this sensitivity. It is found that the complete neglect of these 2-electron processes introduces a large error but once included, the key physical properties are quite insensitive to the rate over the important 2–3 keV temperature range. The high-energy emissivity depends strongly on temperature, peaking at conditions corresponding to a closed shell system, and on the square of the electron density, as for a coronal system.     

Photoionization and detection of ultracold Cs<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> molecules through diffuse bands

We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms. The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs₂ diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules. Received 13 September 2001     

An ab initio potential energy surface and spectroscopic constants for the XΣg state of NO2

A three-dimensional potential energy function has been calculated for the X¹Σ⁺_g state of NO⁺₂ from ab initio MRD-CI data. With this PE function, converged vibrational calculations have also been performed for ten vibrational states, with the aid of a computer program developed in the present work for this purpose. The calculated harmonic frequencies, vibrational term values and rotational constants are in good agreement with experimental data.     

Photorecombination of Ar-like gallium and germanium ions

The most up-to-date photorecombination spectrum of Ga¹³⁺ and Ge¹⁴⁺ has been re-assessed with direct large-scale relativistic atomic structure calculations. The new temperature-dependent dielectronic recombination rate coefficients are presented in a form convenient for astrophysical plasma modeling, summarizing the importance of different multi-electron intra-shell core excitations in the target ions. Obtained results are expected to facilitate a more accurate determination of the ionization-recombination balance of multiply-charged gallium and germanium ions and to improve the diagnosis of the radiative energy loss rates from low-density high-temperature plasmas.     

Spectroscopic characterization of the potential energy functions of Ne2 Rydberg states in the vicinity of the Ne(S0) + Ne(4p′) dissociation limits

The gerade autoionizing Rydberg states of Ne₂ have been studied in the range 162 000-172 000 cm⁻¹ by 1 + 1′ resonant two-photon excitation from the Ne₂ X ground state via different vibrational levels of the Ne₂ C state. A rotationally resolved part of the spectrum allowed the determination of the potential energy functions of two states of 1_g and characters in the vicinity of the Ne(2p⁶¹S₀) + Ne (2p⁵4p′) dissociation limit. The presence of maxima in these potential energy functions is interpreted as originating from a repulsive interaction between the Rydberg electron and the neutral atom.     

Vibrational wave packet dynamics in the silver tetramer probed by NeNePo femtosecond pump-probe spectroscopy

We present results on the ultrafast dynamics of mass-selected neutral Ag₄ clusters using NeNePo (negative ion - neutral - positive ion) femtosecond pump-probe spectroscopy. One-color pump-probe spectra of the Ag₄ ^-/Ag₄/Ag₄ ⁺ system measured at 385 nm and an internal cluster temperature of 20 K display a complex beat structure over more than 60 ps. The oscillatory structure is attributed to vibrational wave packet dynamics in an excited “dark" state of neutral Ag₄. A dominant 740 fs wave packet period as well as wave packet dephasing and rephasing are observed in the spectra. Fourier analysis of the spectra yields a group of frequencies centered around 45 cm^-1 and an anharmonicity χ _e2νχ _eχ _e of 2.65 cm^-1 for the active vibrational mode. Received 30 November 2000     

Investigation of auto-ionizing states in xenon by resonantly enhanced multi-photon ionization

We have examined the autoionization spectrum of xenon by resonantly enhanced three-photon ionization (2 + 1 REMPI) involving intermediate states 5p ⁵6p[J = 0, 2]. The properties of the observed autoionization resonances change significantly with the choice of the intermediate state. For ionization via an intermediate state with predominantly 5p ⁵(²P_3/2) core character, a strong continuum with embedded window-type 5p ⁵(²P _1/2)nd'-autoionization resonances is observed. For intermediate states, predominantly with 5p ⁵(²P_1/2) core character, both 5p ⁵(²P _1/2)nd'- as well as 5p ⁵(²P _1/2)ns'-resonances are present in the spectrum as overlapping, nearly symmetric peaks on a rather weak continuum. Calculations confirm the significant dependence of the spectral lineshapes upon the excitation pathway to the autoionizing state. The ionization data are compared with spectra obtained by monitoring third-harmonic generation via autoionizing states without resonant excitation of intermediate states. These spectra also exhibit the signature of both the nd'- and ns'-resonances. Received 30 September 2002 Published online 28 January 2003 RID="a" ID="a"Permanent address: Rostov State University of Transport Communication, 344038, Rostov-on-Don, Russia. RID="b" ID="b"e-mail: halfmann@physik.uni-kl.de     

Co-like Au52+离子双电子复合的理论研究

基于准相对论Hatree-Fock理论,采用Cowan程序详细计算了Co-like A u52+离子的双电子复合速率系数、自电离几率以及自电离能级.计算结果表明:由于径向波函数的穿透效应使得该离子自电离能级3d84l5s(l=s、 p、d、f)升高,造成能级间隔不随外层激发电子轨道角动量的增加单调减小的异常现象,即Δ(E3d8 4l5d-E3d84l5p)＞Δ(E3d84l5p-E3d84l5s)＞Δ(E 3d84l5f-E3d84l5d);双激发自电离态平均自电离几率具有特定的变化关系;双电子复合速率系数随着电子温度逐渐增加具有共振、高温收敛等特点,且双激发态轨道角动量大且宇称为奇的通道复合速率系数较大,其中辐射衰变通道为3d84fnd-3d9nd 的复合过程占优势,在Te=0.49*"KeV时共振峰αDR=1.01×10-11(cm 3sec-1).     

Doubly excited states in the negative hydrogen ion

We present a detailed analysis of doubly excited resonances in H^- of both and symmetry. Both resonance positions and total widths for auto-detachment are calculated using complex coordinate scaling in a Sturmian-type basis in perimetric coordinates. The resonances are classified by approximate quantum numbers with help of their Lewis structures. For the first time, a new class of shape resonances is reported which can be understood as resulting from couplings between different adiabatic potentials with both binding and repulsive character. In addition, we present an analysis of the so called mass polarisation term which gives rise to specific isotope shifts. Received 10 March 1999 and Received in final form 18 October 1999     

Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase

在分子坐标系中光电子角度分布(MFPADs)的层次上,对D2分子用SOLEIL的真空紫外同步辐射圆偏振光诱发的共振和非共振光电离进行了比较研究. 采用结合了成像与飞行时间分辨的电子离子符合技术的矢量相关方法,以及用于表示MFPADs的强度I(χ,θe, φe)的通用形式. 其中χ是分子轴与光量子化方向之间的夹角,(θe,φe)是分子坐标系中电子的发射方向. 研究了D2分子在双光子激发能量下的解离光电离(DPI),在hⅴ=19 eV下直接光电离是唯一通道的情况,以及在hⅴ=32.5 eV对应于Q1和Q2双激