Investigation of odd-parity Rydberg states of Eu I with autoionization detection

Isolated-core-excitation （ICE） scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f76s6p[8Ph/2], 4f76s6p[8P7/2] and 4f76s6p[SP9/2] intermediate states, respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000 cm-1 to 38250 cm-1 and from 38900 cm-1 to 39500 cm-1. The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n＊ for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.

The chaotic property in the autoionization of Rydberg lithium atom

This paper presents theoretical computations of the ionization rate of Rydberg lithium atom above the classical ionization threshold using semiclassical approximation. The yielded random pulse trains of the escape electrons are recorded as a function of emission time such that they can be related to the terms of the recurrence periods of the photoabsorption. This fact illustrates that it is ionic core scattering processes which give rise to chaos in autoionization dynamics and this is verified by comparison of our results with the hydrogen atom situation. In order to reveal the chaotic properties in detail, the sensitive dependence of the ionization rate upon the scaled energy is discussed for different scaled energies. This approach provides a simple explanation for the chaotic character in autoionization decay of Rydberg alkali-metal atoms.

Investigation of autoionization spectra of Sm atoms using an isolated-core excitation method

Using the isolated-core-excitation scheme and three-step laser resonance ionization spectroscopy approach, this paper, for the first time, has systematically investigated the autoionization spectra of atomic Sm, belonging to the 4f^6 6pn/ and 4f^5 5d6sn/ （l = 0,2） configurations. In the experiment, the first two tunable dye lasers are employed to excite the Sm atom from its initial state to the different 4f^6 6sn/ bound Rydberg states, then the third dye laser is scanned to drive the atom to the doubly-excited autoionizing states. With the above excitation scheme, the measured transition profiles of the autoionizing states are nearly symmetric, from which the level energies and widths can be easily obtained.

Branching ratios of autoionization from Eu 4f^76p_(1/2)6d [J] autoionizing states

The autoionization branching ratios from Eu 4f76p1/26 d [J] autoionizing states to its 4f76s+(9So), 4f76s+(7So), and4f75d+(9Do) final ionic states are investigated with the combination of the three-step laser excitation and the velocity-map imaging technique. These different autoionizing states are excited via 4f76s6d8 DJ [J = 5/2, 7/2, and 9/2] intermediate states, respectively. The experimental photoelectron images are obtained, from which energy distributions of ejected electrons are achieved with the mathematical transformation. Furthermore, the energy dependence of the branching ratio is investigated within the autoionization resonance, by which population inversion is observed as an important characteristic.The J-dependence is also studied systematically. The validity of the well-known isolated core excitation technique used for obtaining the autoionization spectrum is also studied.

A numerical Hartree self-consistent field calculation of an autoionization resonance parameters for a doubly excited 2s^2, 3s^2, and 4s^2 states of He atom with a complex absorbing potential

The self-consistent Hartree-Fock equation for the He atom is solved using the pseudospectral method. The Feshbach- type autoionization resonance parameters for doubly excited 2s2, 3s2, and 4s2 IS states of He have been determined by adding a complex absorbing potential to the Hamiltonian. The Riss-Meyer iterative and Pad6 extrapolation methods are applied to obtain reliable values for the autoionization resonance parameters, which are compared to previous results in the literature.

Theoretical analysis of ionic autoionization spectra of lanthanum via an intermediate state [Xe]5d6d 1P1

In the framework of multi-channel quantum defect theory, eigenquantum defects μα and the transformation matrices Uiα of La＋ are calculated from first principles by relativistic multi-channel theory, while the dipole matrix elements DCr are obtained by fitting with experimental data. Then the ionic autoionization spectra of lanthanum via the intermediate state [Xe]5d6d 1p1 in the energy region of 90213-91905 cm-1 axe obtained. Experimental peaks are classified and assigned by comparing with the corresponding calculated spectra. More specifically, four ionic autoionization Rydberg series converging to La2＋ 5d5/2 2D5/2 and several states converging to higher lying states of La2＋ are found and assigned.

Detailed Theoretical Investigations on the L-Shell Absorption of Open-M-Shell Germanium Plasmas:Effect of Autoionization Resonance Broadening

Radiative opacity of open-M-shell germanium plasmas in the L-shell photon energy region were investigated in detail by using a fully relativistic detailed level accounting approach. Among other physical effects such as relativistic and the interaction between fine-structure levels belonging to the same non-relativistic configuration and different configurations, particular attention is paid on the effect of autoionization resonance broadening on the L-shell absorption. The results show that for plasmas at present and past typical experimental conditions, line width due to autoionization resonance broadening dominate among all the physical broadening mechanisms including electron impact and Doppler broadenings. Such an effect is most pronounced for ions with just a few 2p-nd transition lines such as Ge14+, while it is not so pronounced for complex ions such as Ge16+, where there are so many 2p-nd lines that line overlapping partly conceal the effect of autoionization resonance broadening. After taking the effect of autoionization resonance broadening into account, detailed comparisons are made with available experimental spectra at different physical conditions of different plasma temperatures and densities. The L-shell absorption is sensitive to the plasma temperature, especially in the 2p-3d excitation energy region. The potential of utlizing the relative shape and intensity of the 2p-3d spin-orbit splitting as temperature diagnostics is investigated.

Saturation effects on Ba 6phi （l=0, 2） and 6pnk （｜M｜= 0, 1） autoionization spectra

Using a three-step laser saturation excitation technique, the saturation effects on the Ba 6pns （J = 1） and 6pad （J = 1, 3） autoionization spectra are observed systemically in zero field. These saturation spectra are introduced to determine the high n members of 6pnl （l = 0, 2） autoionizing series and are used to analyse the channel interactions among the autoionizing series in zero field. Furthermore, the saturation excitation technique is applied to the electric field case, in which the saturation spectra of Ba 6pnk （｜M｜= 0, 1） autoionizing Stark states are measured. Most of these saturation spectra are observed for the first time so far as we know, which indicate the mixing of the autoionizing states in the electric fields.

Autoionization spectra of Sm atom

Spectra of autoionizing states of the Sm atom in an energy region between 45948.9 cm^-1 and 46943.6 cm^-1 are systematically investigated by a three-color multi-step resonant excitation scheme with three different excitation paths.The three intermediate states,4f 66s7s 7F3,4f 66s7s 7F4,and 4f 66s7s 9F5 are employed for the three paths,respectively.Based on precise calibration of wavelength,the level energies of 112 autoionizing states are determined with the line widths and the relative line intensities of the related transitions.The possible influence of configuration interaction on the line shape of autoionizing state is also discussed.In addition,a unique value of J,the total angular momentum,is assigned to all detected states by comparing the three spectra obtained with the different excitation paths.

Two-color spectroscopy of UV excited ssDNA complex with a single-wall nanotube photoluminescence probe： Fast relaxation by nucleobase autoionization mechanism

DNA autoionization is a fundamental process wherein ultraviolet （UV）- photoexcited nucleobases dissipate energy by charge transfer to the environment without undergoing chemical damage. Here, single-wall carbon nanotubes （SWNT） are explored as a photoluminescent reporter for the study of the mechanism and rates of DNA autoionization. Two-color photoluminescence spectroscopy allows separate photoexcitation of the DNA and the SWNTs in the UV and visible range, respectively. A strong SWNT photoluminescence quenching is observed when the UV pump is resonant with the DNA absorption, consistent with charge transfer from the excited states of the DNA to the SWNT. Semiempirical calculations of the DNA-SWNT electronic structure, combined with a Green＇s function theory for charge transfer, show a 20 fs autoionization rate, dominated by hole transfer. Rate-equation analysis of the spectroscopy data confirms that the quenching rate is limited by thermalization of the free charge carriers transferred to the nanotube reservoir. This approach has great potential for monitoring DNA excitation, autoionization, and chemical damage, both in vivo and in vitro.

Variational Calculations for (ns2) 1Se, (np2) 1De and (nd2) 1Ge Resonance States for He Isoelectronic Sequences below the n = 2, 3 and 4 Hydrogenic Thresholds

This work presents results of the different parameters which characterize the nonrelativistic Hamilton operator for the helium atoms allowing us to solve the Schrödinger equation. The total energy is decomposed into three terms allowing to separate the kinetic energy, the electrons-nucleus interaction energy and the electron-electron interaction energy of the (2s2, 3s2 and 4s2) 1Se, (2p2, 3p2 and 4p2) 1De and (3d2 and 4d2) 1Ge resonance singlet states of the helium isoelectronic sequences. The states have been defined by using special forms of the Hylleraas type wave functions. The calculations have been carried out in the framework of the variational method using configuration interaction basis states with a real Hamiltonian. The agreement of the energy value of other states between the present theoretical values available in the literature is excellent. But as for the comparison of the kinetic energies, the electrons-nucleus energies interaction and the electron-electron interaction energies, we note a slight difference with the theoretical values common in literature.

The effect of configuration complex on dielectronic recombination process in highly ionized plasmas

This paper analyses the effect of configuration complex on dielectronic recombination （DR） process in highly ionized plasmas （Xe^26＋, Dy^38＋, W^46＋） by using the multiconfiguration relativistic Hartree-Fock method. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The remarkable difference between the isoelectronic trend of the rate coefficients for DR through 3d^94l4l′ and through 3d^94l5l′ is emphasized. The trend of DR through 3d^94l4l′ shows irregularities at relatively low temperature due to the progressive closing of DR channels as atomic number Z increases.

Energy Positions of the ^1,3D^eRydberg Series of the He-Like Ions Up to the <i>N</i>= 9 Threshold

The doubly excited states of helium-like ions are investigated using a combination of the no-linear parameters of Hylleraas and the β-parameters of screening constant by unit nuclear charge. Calculations are performed for total energies of low-lying doubly excited states (N = 2 - 9) in He-like ions up to Z = 10. The results obtained from the novel method are in good agreement with the available theoretical calculations and experimental observations.

The VMI study on angular distribution of ejected electrons from Eu 4f^76p_(1/2)6d autoionizing states

The combination of a velocity mapping imaging technique and mathematical transformation is adopted to study the angular distribution of electrons ejected from the Eu 4f76p1/26 d autoionizing states, which are excited with a three-step excitation scheme via different Eu 4f76s6d8 D J（J = 5/2, 7/2, and 9/2） intermediate states. In order to determine the energy dependence of angular distribution of the ejected electrons, the anisotropic parameters are measured in the spectral profile of the 6p1/26 d autoionizing states by tuning the wavelength of the third-step laser across the ionic resonance lines of the Eu 6s＋→ 6p＋. The configuration interaction is discussed by comparing the angular distributions of ejected electrons from the different states. The present study reveals the profound variations of anisotropic parameters in the entire region of autoionization resonance, highlighting the complicated nature of the autoionization process for the lowest member of6p1/26 d autoionization series.

Experimental study of bound and autoionizing Rydberg states of the europium atom

An isolated-core-excitation （ICE） scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400-43500 cm^-1 is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f^76pnl（l = 0, 2） configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy （RIS） approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.

TERM ENERGIES FOR THE AUTOIONIZING STATES OF THE LITHIUM ATOM

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Theoretical Analysis of Rydberg and Autoionizing State Spectra of Antimony

We calculate the Rydberg and autoionization Rydberg spectra of antimony （Sb） from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can be used to classify and assign the atomic states described in recently reported three Rydberg series and four autoionizing states. The perturbation effects on line intensity, variation and line profile are discussed. Assignments of the perturber states and autoionizing states are presented.

Modified atomic orbital theory applied to the calculation of high-lying ₂(K,T)_n^±1,3P°rydberg series of he-like ions

The 2(1,0)n-1P°, 2(1,0)n +3P°, 2(0,1)n+1P°, and 2(0,1)n-3P° intershell Rydberg series of the helium-like ions are investigated in the framework of the modified Atomic Orbital Theory (MAOT). High-lying energy resonances of He and excitation energy of the he- lium-like Li+ up to n = 10 are tabulated. In addition, total energy positions for low-lying states (n1,3P° autoionizing states of two-electron systems.

OBSERVATION OF RYDBERG AUTOIONIZING STATE OF CS_2 AND HIGHER EXCITED VIBRATIONAL STATE OF CS_2^+

I. INTRODUCTION In recent years, the investigation of autoionization processes attracts much attention as MPI （multiphoton Ionization）spectroscopy has developed rapidly. However, much work has been done on atomic system. In comparison, the molecules have richer vibronic structure which makes the research more complicated. Great attention has been given to the MPI study of CS2 and CS2+. One of the reasons is that the CS2 mole-

High-resolution dipole (e, e) study for optical oscillator strengths of helium

The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurement have been avoided and the experimental precision has been improved by using this method. The optical oscillator strength density spectrum corresponding to the 1S n’P transitions and ionization of helium has been measured in the energy loss range of 21 - 26 eV. And the same work corresponding to the autoionization resonance region has been done in energy loss ranges of 59-67 eV and 69-74 eV. The above results have also been compared with those of the previous work.