A new electron impact storage ion source has been designed for time of flight mass spectrometers with a high mass resolving power and high sensitivity. Because of the storage and compressing focus of the source, the o...A new electron impact storage ion source has been designed for time of flight mass spectrometers with a high mass resolving power and high sensitivity. Because of the storage and compressing focus of the source, the overall performance of the instrument has been improved greatly with a mass resolving power up to 3 500. The conditions of the second order of the focus are given and the storage ability is proved. The competer simulations and experiment results are given, too.展开更多
Fully differential cross sections （FDCS） are calculated within a four-body model for single ionization of helium by C6＋ impact at the incident energy of 100 MeV/a.u. （atomic unit）. The results are compared with e...Fully differential cross sections （FDCS） are calculated within a four-body model for single ionization of helium by C6＋ impact at the incident energy of 100 MeV/a.u. （atomic unit）. The results are compared with experimental data and other theoretical predictions. It is shown that our results are in very good agreement with experiment for three small momentum transfers in the scattering plane; however, some significant discrepancies are still present at the largest momentum transfer in both the scattering plane and the perpendicular plane. In actuality, the problem has not been explained by the theory during the last decade. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that for the largest momentum transfer the cross section arising from a destructive interference of the three amplitudes is much smaller than the experimental data. However, the cross section due to the constructive interference of two scattering amplitudes between projectile-ionized electron interaction and projectile-passive electron interaction almost approaches the experimental data.展开更多
Electron-impact single ionization cross sections for W^q＋（q = 4–5） were calculated using the flexible atomic code（FAC） in the level-to-level distorted-wave method, considering the explicit branching ratio. The c...Electron-impact single ionization cross sections for W^q＋（q = 4–5） were calculated using the flexible atomic code（FAC） in the level-to-level distorted-wave method, considering the explicit branching ratio. The calculated cross sections are compared with the available theoretical and experiment results in detail. In the case of the contribution from the same channles as the available theoretical results, all of the calculated ionization cross sections agree with the experimental measured cross sections. But the present calculated results are larger than the experimental measurement when all channels contributions are included. Some important channels excitation autoionization（EA） contributions, such as the excitation to higher higher nl subshell from 4 f and 5[s,p], were not included into the available theoretical calculation. In general, the distorted-wave（DW） results are overestimated.展开更多
The ionization process in the collisions of He^2＋ with C^q＋ （q = 0-5） is investigated by using the continuum-distorted-wave eikonal-initial-state approximation. Double-differential cross sections for 1s and 2s sub...The ionization process in the collisions of He^2＋ with C^q＋ （q = 0-5） is investigated by using the continuum-distorted-wave eikonal-initial-state approximation. Double-differential cross sections for 1s and 2s sub-shells are obtained at the electron-ejected angle θ = 0° with the projectile energy ranging from 30keV/u to 10MeV/u. Variation of ionization mechanisms with q in C^q＋ is studied, and the dependences on the projectile energies and target sub-shells are also discussed. It is found that in the whole energy range, the absolute values of soft collision （SC） and binary encounter （BE） peaks decrease with increasing q. For the lower incident energies, the electron capture to the projectile continuum （ECC） peak decrease with increasing q as well as SC and BE peaks. For the higher incident energies （〉 1 MeV/u）, the absolute value of ECC peak increases with increasing q, so that the crossings of cross sections appear for C^q＋ with different q. This can be explained by the matching of velocities between the projectile and the electron initially bound to the target.展开更多
The three-Coulomb-wave （3C） model is applied to study the single ionization of helium by 2 MeV/amu C6＋ impact. Fully differential cross sections （FDCS） are calculated in the scattering plane and the results are c...The three-Coulomb-wave （3C） model is applied to study the single ionization of helium by 2 MeV/amu C6＋ impact. Fully differential cross sections （FDCS） are calculated in the scattering plane and the results are compared with experimental data and other theoretical predictions. It is shown that the 3C results of the recoil peak are in very good agreement with experimental observations, and variation of the position of the binary peak with increasing momentum transfer also conforms better to the experimental results. Furthermore, the contributions of different scat- tering amplitudes are discussed. It turns out that the cross sections are strongly influenced by the interference of these amplitudes.展开更多
The multi-charged sulfur ions of Sq^＋ （q ≤ 6） have been generated when hydrogen sulfide cluster beams are irradiated by a nanosecond laser of 1064 and 532 nm with an intensity of 10^10- 10^12W.cm^-2. S^6＋ is the ...The multi-charged sulfur ions of Sq^＋ （q ≤ 6） have been generated when hydrogen sulfide cluster beams are irradiated by a nanosecond laser of 1064 and 532 nm with an intensity of 10^10- 10^12W.cm^-2. S^6＋ is the dominant multicharged species at 1064 nm, while S^4＋, S^3＋ and S^2＋ ions are the main multi-charged species at 532 nm. A three-step model （i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing） is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2,λA being the laser wavelength.展开更多
A four-body distorted wave approximation is presented for theoretical investigations of the single ionization of groundstate helium atoms by fully stripped carbon ions at impact energies of 2 MeV/amu and 100 MeV/amu. ...A four-body distorted wave approximation is presented for theoretical investigations of the single ionization of groundstate helium atoms by fully stripped carbon ions at impact energies of 2 MeV/amu and 100 MeV/amu. The nine-dimensional integrals for the partial quantum-mechanical transition amplitudes of the specified reaction are reduced to some analytical expressions or one-dimensional integrals over real variables. Fully differential cross sections（FDCSs） are calculated and compared with their experimental values as well as the results obtained from other theories. Despite the simplicity and quickness of the proposed quadrature, the comparison shows that the obtained results are in reasonable agreement with the experiment and are compatible with those of other complicated theories.展开更多
In time-of-flight mass spectrometry（TOF MS）, superconducting strip ion detectors（SSIDs） in the parallel configuration are promising for ideal ion detection with a nanosecond-scale time response and a practical lar...In time-of-flight mass spectrometry（TOF MS）, superconducting strip ion detectors（SSIDs） in the parallel configuration are promising for ideal ion detection with a nanosecond-scale time response and a practical large sensitive area. In the parallel configuration, the bias current in one strip is diverted into other parallel strips after each detection event. Under high bias current conditions, the diverted bias current induces cascade switching of all parallel strips. Studies show that cascade switching degrades the ion count rate of SSIDs made from niobium and hence is disliked in TOF MS applications. To suppress the bias current redistribution, we connected resistors in a series with the individual parallel strips using aluminum-bonding wires. Their effect was studied by measuring the pulse height distributions.展开更多
文摘A new electron impact storage ion source has been designed for time of flight mass spectrometers with a high mass resolving power and high sensitivity. Because of the storage and compressing focus of the source, the overall performance of the instrument has been improved greatly with a mass resolving power up to 3 500. The conditions of the second order of the focus are given and the storage ability is proved. The competer simulations and experiment results are given, too.
基金supported by the National Natural Science Foundation of China(Grant No.11274215)the Natural Science Foundation of Shanxi Province,China(Grants Nos.20051008 and 2010011009)the Technology Project of Shanxi Provincial Education Department,China(Grant No.20111011)
文摘Fully differential cross sections （FDCS） are calculated within a four-body model for single ionization of helium by C6＋ impact at the incident energy of 100 MeV/a.u. （atomic unit）. The results are compared with experimental data and other theoretical predictions. It is shown that our results are in very good agreement with experiment for three small momentum transfers in the scattering plane; however, some significant discrepancies are still present at the largest momentum transfer in both the scattering plane and the perpendicular plane. In actuality, the problem has not been explained by the theory during the last decade. Accordingly, the contributions of different scattering amplitudes to FDCS are analyzed. It is found that for the largest momentum transfer the cross section arising from a destructive interference of the three amplitudes is much smaller than the experimental data. However, the cross section due to the constructive interference of two scattering amplitudes between projectile-ionized electron interaction and projectile-passive electron interaction almost approaches the experimental data.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.2017YFA0402300,11464042,11564036,11774292,and 11464040)the Basic Scientific Research Foundation for Institution of Higher Learning of Gansu Province,China
文摘Electron-impact single ionization cross sections for W^q＋（q = 4–5） were calculated using the flexible atomic code（FAC） in the level-to-level distorted-wave method, considering the explicit branching ratio. The calculated cross sections are compared with the available theoretical and experiment results in detail. In the case of the contribution from the same channles as the available theoretical results, all of the calculated ionization cross sections agree with the experimental measured cross sections. But the present calculated results are larger than the experimental measurement when all channels contributions are included. Some important channels excitation autoionization（EA） contributions, such as the excitation to higher higher nl subshell from 4 f and 5[s,p], were not included into the available theoretical calculation. In general, the distorted-wave（DW） results are overestimated.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10574018 and 10574020, the Science and Technology Foundation of Chinese Academy of Engineering Physics and National High-Tech ICF Committee in China.
文摘The ionization process in the collisions of He^2＋ with C^q＋ （q = 0-5） is investigated by using the continuum-distorted-wave eikonal-initial-state approximation. Double-differential cross sections for 1s and 2s sub-shells are obtained at the electron-ejected angle θ = 0° with the projectile energy ranging from 30keV/u to 10MeV/u. Variation of ionization mechanisms with q in C^q＋ is studied, and the dependences on the projectile energies and target sub-shells are also discussed. It is found that in the whole energy range, the absolute values of soft collision （SC） and binary encounter （BE） peaks decrease with increasing q. For the lower incident energies, the electron capture to the projectile continuum （ECC） peak decrease with increasing q as well as SC and BE peaks. For the higher incident energies （〉 1 MeV/u）, the absolute value of ECC peak increases with increasing q, so that the crossings of cross sections appear for C^q＋ with different q. This can be explained by the matching of velocities between the projectile and the electron initially bound to the target.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11274215)the Natural Science Foundation of Shanxi Province,China (Grant Nos. 20051008 and 2010011009)the Technology Project of Shanxi Provincial Education Department,China (Grant No. 20111011)
文摘The three-Coulomb-wave （3C） model is applied to study the single ionization of helium by 2 MeV/amu C6＋ impact. Fully differential cross sections （FDCS） are calculated in the scattering plane and the results are compared with experimental data and other theoretical predictions. It is shown that the 3C results of the recoil peak are in very good agreement with experimental observations, and variation of the position of the binary peak with increasing momentum transfer also conforms better to the experimental results. Furthermore, the contributions of different scat- tering amplitudes are discussed. It turns out that the cross sections are strongly influenced by the interference of these amplitudes.
基金Project supported by the National Natural Science Foundation of China （Grant No 20573111） and partly supported by the Center for Computational Science, Hefei Institutes of Physical Sciences, China （Grant No 0331405002）.
文摘The multi-charged sulfur ions of Sq^＋ （q ≤ 6） have been generated when hydrogen sulfide cluster beams are irradiated by a nanosecond laser of 1064 and 532 nm with an intensity of 10^10- 10^12W.cm^-2. S^6＋ is the dominant multicharged species at 1064 nm, while S^4＋, S^3＋ and S^2＋ ions are the main multi-charged species at 532 nm. A three-step model （i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing） is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2,λA being the laser wavelength.
基金the office of graduate studies at the University of Isfahan for their support and research facilities
文摘A four-body distorted wave approximation is presented for theoretical investigations of the single ionization of groundstate helium atoms by fully stripped carbon ions at impact energies of 2 MeV/amu and 100 MeV/amu. The nine-dimensional integrals for the partial quantum-mechanical transition amplitudes of the specified reaction are reduced to some analytical expressions or one-dimensional integrals over real variables. Fully differential cross sections（FDCSs） are calculated and compared with their experimental values as well as the results obtained from other theories. Despite the simplicity and quickness of the proposed quadrature, the comparison shows that the obtained results are in reasonable agreement with the experiment and are compatible with those of other complicated theories.
基金Project supported by a Grant-in-Aid for Scientific Research (A) and (C) from the Japan Society for the Promotion of Science(Grant Nos.22246056 and 24619013)
文摘In time-of-flight mass spectrometry（TOF MS）, superconducting strip ion detectors（SSIDs） in the parallel configuration are promising for ideal ion detection with a nanosecond-scale time response and a practical large sensitive area. In the parallel configuration, the bias current in one strip is diverted into other parallel strips after each detection event. Under high bias current conditions, the diverted bias current induces cascade switching of all parallel strips. Studies show that cascade switching degrades the ion count rate of SSIDs made from niobium and hence is disliked in TOF MS applications. To suppress the bias current redistribution, we connected resistors in a series with the individual parallel strips using aluminum-bonding wires. Their effect was studied by measuring the pulse height distributions.
