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 ...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.展开更多
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 excitati...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.展开更多
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 ...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.展开更多
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 ...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.展开更多
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 ...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.展开更多
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 exc...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.展开更多
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 d...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.展开更多
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 ele...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.展开更多
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, belon...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.展开更多
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 met...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.展开更多
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 bee...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.展开更多
Ionic Rydberg energy levels of lanthanum are calculated from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. The present calculated results are in bette...Ionic Rydberg energy levels of lanthanum are calculated from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. The present calculated results are in better agreement with the experimental measurements than the previous calculations [J. Phys. B 34 （2001）369] due to the consideration of dynamical polarizations. Moreover, in the experimental spectra achieved by a five-laser resonance excitation via the intermediate state 5d6d^3 F2, a series of weak ionic Rydberg states and some of perturbing states are found and assigned in this work.展开更多
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 dipo...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.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11174218)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.11174218)
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10574098 and 10674102)the Natural Science Foundation of Tianjin,China (Grant No.05YFJMJC05200)
文摘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.
基金Supported by the Beijing Natural Science Foundation under Grant No 1164016the National Natural Science Foundation of China under Grant No 11604334the Funding from TRIUMF which receives Federal Funding via a Contribution Agreement with the National Research Council of Canada and through a Natural Sciences and Engineering Research Council of Canada under Grant No 386343-2011
文摘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.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574098）, the Natural Science Foundation , （Grant No 05YFJMJC05200） of Tianjin, and the Scientific Research Fund of Zhejlang Provincial Education Department.
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11174218 and 10674102)the Natural Science Foundation of Tianjin,China (Grant No. 05YFJMJC05200)
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574098, 10674102)the Natural Science Foundation of Tianjin (Grant No 05YFJMJC05200)
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10774093 and 10374061)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos 10574098 and 10674102)the Natural Science Foundation of Tianjin of China(Grant No 05YFJMJC05200)
文摘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.
基金supported by the National Natural Science Foundation of China (Grant No 60054402)
文摘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.
文摘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.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10574162, 10676014, 10674021 and 90508001, the Scientific Research Fund of Graduate University of the Chinese Academy of Sciences under Grant No 055101BM03, the Ministry of Education of China under Grant No 306020, the Hi-Tech Research and Development Programme of China under Grant No 2006AA02Z472, and the National Key Basic Research Programme of China under Grant No 2005CB724500.
文摘Ionic Rydberg energy levels of lanthanum are calculated from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. The present calculated results are in better agreement with the experimental measurements than the previous calculations [J. Phys. B 34 （2001）369] due to the consideration of dynamical polarizations. Moreover, in the experimental spectra achieved by a five-laser resonance excitation via the intermediate state 5d6d^3 F2, a series of weak ionic Rydberg states and some of perturbing states are found and assigned in this work.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574162 and 10774186)the Scientific Research Fund of Graduate University of the Chinese Academy of Sciences (Grant No 055101BM03)
文摘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.
