A program is established based on the Monte Carlo technique to simulate the time-of-flight spectrum in ion-atom collisions. The goal of establishing the simulation program is to analyze the distributions of the fragme...A program is established based on the Monte Carlo technique to simulate the time-of-flight spectrum in ion-atom collisions. The goal of establishing the simulation program is to analyze the distributions of the fragments produced in ion-molecule collisions. The program produces the space density distributions of the projectile beam and of the target atomic beam, the initial velocity distribution of target atoms, and the charge states展开更多
Ion-pair dissociation is an important molecular process and frequently happens when the target molecule is pumped to its electronically superexcited states. In contrast to the experimental studies of photoexcitation i...Ion-pair dissociation is an important molecular process and frequently happens when the target molecule is pumped to its electronically superexcited states. In contrast to the experimental studies of photoexcitation ion-pair dissociation, there are some experimental challenges in the electron-impact ion-pair dissociation study, in particular, on determination of the energetic threshold. Here we report an experimental development for the ion-pair dissociation study by using the monochromized electron impacts. As an example, the threshold of BrCN→Br^-+CN^+ is determined as 13.78 eV according to the appearance energy of CN^+ signals, meanwhile, the time-sliced ion velocity image of CN^+ is recorded at 16.09 eV and indicates an anisotropic distribution of the CN^+ momentum.展开更多
Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematicall...Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematically complete experhnent performed for the collision process. Using the so-called list-mode data recording technique and the coincidence measurement, the momentum vector of each fragment from the molecular ion were recorded event by event. The orientation of the molecular axis for H2^＋ dissociation reactions could be determined for each event in the off-line analysis. The measured orientation of the molecular ion is believed the same as the one at the instance of collision under axial recoil approximation. The polar angle resolution of the molecular orientation of ±8° was obtained.展开更多
In conventional ion-atom collision experimental investigations, the fragments produced in the reaction are projected to a simple detector by static electric field. This technique only gives time-of-flight of the fragm...In conventional ion-atom collision experimental investigations, the fragments produced in the reaction are projected to a simple detector by static electric field. This technique only gives time-of-flight of the fragments, consequently one obtains only one-dimension information of the fragment. In order to investigate the complete dynamics of ion-molecule collisions, it is necessary to develop a position-sensitive multi-hit detector system. The position information was obtained by using the wedge-and-strip anode with very good resolution.展开更多
With the experimental data from STAR program on the centrality dependence of the PT spectra of charged hadron produced in d＋Au collisions at √^8NN=200 GeV, we show that there also exists a scaling distribution in th...With the experimental data from STAR program on the centrality dependence of the PT spectra of charged hadron produced in d＋Au collisions at √^8NN=200 GeV, we show that there also exists a scaling distribution in the backward rapidity regions. Using this scaling distribution, we get the theoretical psedorapidity asymmetry which is basically in agreement with STAR data in the regions of 0≤｜η｜≤0.5 and 0.5 ≤｜η｜≤1. No theoretical models are used in any part of this phenomenological analysis.展开更多
The reaction rate coefficient for collision between hydrogen molecular ions and nitrogen molecules has been measured by usingion storage technique.The results are Kpt=5.23×10^-9cm^3/sec for proton transfer and kc...The reaction rate coefficient for collision between hydrogen molecular ions and nitrogen molecules has been measured by usingion storage technique.The results are Kpt=5.23×10^-9cm^3/sec for proton transfer and kct=4.5×10^-10cm^3/sec for charge transfer.展开更多
The influence of the density-dependent symmetry energy on the balance energy （Ebal） of directed flow from heavy ion collisions （HICs） at incident energies covered by INDRA and MSU experiments is studied, using the...The influence of the density-dependent symmetry energy on the balance energy （Ebal） of directed flow from heavy ion collisions （HICs） at incident energies covered by INDRA and MSU experiments is studied, using the updated version of the ultra- relativistic quantum molecular dynamics （UrQMD） model, especially adapted to low-energy heavy ion collisions （HICs）. Four mass-symmetric reactions with total mass numbers between 192 and 394 are chosen for investigating the influence of the symmetry energy on the system-mass dependence of Eual. The results show that the uncertainty in the density dependence of the symmetry potential causes changes of Ebal of the order of several MeV, depending on the type of particle considered. The Ebal of neutrons from HICs is particularly sensitive to the density dependence of the symmetry potential energy, while the system-mass dependence of EbaI of Z = 1 particles is not.展开更多
文摘A program is established based on the Monte Carlo technique to simulate the time-of-flight spectrum in ion-atom collisions. The goal of establishing the simulation program is to analyze the distributions of the fragments produced in ion-molecule collisions. The program produces the space density distributions of the projectile beam and of the target atomic beam, the initial velocity distribution of target atoms, and the charge states
基金supported by the National Natural Science Foundation of China (No.21625301)
文摘Ion-pair dissociation is an important molecular process and frequently happens when the target molecule is pumped to its electronically superexcited states. In contrast to the experimental studies of photoexcitation ion-pair dissociation, there are some experimental challenges in the electron-impact ion-pair dissociation study, in particular, on determination of the energetic threshold. Here we report an experimental development for the ion-pair dissociation study by using the monochromized electron impacts. As an example, the threshold of BrCN→Br^-+CN^+ is determined as 13.78 eV according to the appearance energy of CN^+ signals, meanwhile, the time-sliced ion velocity image of CN^+ is recorded at 16.09 eV and indicates an anisotropic distribution of the CN^+ momentum.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10434100） and the Knowledge Innovation Project of Chinese Academy of Sciences.
文摘Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematically complete experhnent performed for the collision process. Using the so-called list-mode data recording technique and the coincidence measurement, the momentum vector of each fragment from the molecular ion were recorded event by event. The orientation of the molecular axis for H2^＋ dissociation reactions could be determined for each event in the off-line analysis. The measured orientation of the molecular ion is believed the same as the one at the instance of collision under axial recoil approximation. The polar angle resolution of the molecular orientation of ±8° was obtained.
文摘In conventional ion-atom collision experimental investigations, the fragments produced in the reaction are projected to a simple detector by static electric field. This technique only gives time-of-flight of the fragments, consequently one obtains only one-dimension information of the fragment. In order to investigate the complete dynamics of ion-molecule collisions, it is necessary to develop a position-sensitive multi-hit detector system. The position information was obtained by using the wedge-and-strip anode with very good resolution.
基金National Natural Science Foundation of China under Grant No.10777577
文摘With the experimental data from STAR program on the centrality dependence of the PT spectra of charged hadron produced in d＋Au collisions at √^8NN=200 GeV, we show that there also exists a scaling distribution in the backward rapidity regions. Using this scaling distribution, we get the theoretical psedorapidity asymmetry which is basically in agreement with STAR data in the regions of 0≤｜η｜≤0.5 and 0.5 ≤｜η｜≤1. No theoretical models are used in any part of this phenomenological analysis.
基金The Project Supported by National Natural Science Foundation of China
文摘The reaction rate coefficient for collision between hydrogen molecular ions and nitrogen molecules has been measured by usingion storage technique.The results are Kpt=5.23×10^-9cm^3/sec for proton transfer and kct=4.5×10^-10cm^3/sec for charge transfer.
基金supported in part by the Key Project of the Ministry of Education of China (Grant No.209053)the National Natural Science Foundation of China (Grant Nos.10905021 and 10979023)+2 种基金the Zhejiang Provincial Natural Science Foundation of China (Grant No.Y6090210)the Qianjiang Talents Project of Zhejiang Province (Grant No.2010R10102)the Department of Education of Liaoning Province (Grant No.L2010521)
文摘The influence of the density-dependent symmetry energy on the balance energy （Ebal） of directed flow from heavy ion collisions （HICs） at incident energies covered by INDRA and MSU experiments is studied, using the updated version of the ultra- relativistic quantum molecular dynamics （UrQMD） model, especially adapted to low-energy heavy ion collisions （HICs）. Four mass-symmetric reactions with total mass numbers between 192 and 394 are chosen for investigating the influence of the symmetry energy on the system-mass dependence of Eual. The results show that the uncertainty in the density dependence of the symmetry potential causes changes of Ebal of the order of several MeV, depending on the type of particle considered. The Ebal of neutrons from HICs is particularly sensitive to the density dependence of the symmetry potential energy, while the system-mass dependence of EbaI of Z = 1 particles is not.
