The electron capture of Gamow--Teller transition on iron group nuclei is investigated in a strong magnetic. field at the crusts of neutron stars. The results show that the magnetic field has only a slight effect on th...The electron capture of Gamow--Teller transition on iron group nuclei is investigated in a strong magnetic. field at the crusts of neutron stars. The results show that the magnetic field has only a slight effect on the electron capture rates with the range of the magnetic fields （10^9 - 10^13 G） on surfaces of most neutron stars, whereas for some magnetars whose range of the magnetic field is 10^13 - 10^18 G, the electron capture rates of most iron group nuclei would be debased greatly and may be even decreased overrun 3 orders of magnitude by the strong magnetic field.展开更多
Dynamic nuclear polarization （DNP） has become a very important hyperpolarization method because it can dramatically increase the sensitivity of nuclear magnetic resonance （NMR） of various molecules. Liquid-state D...Dynamic nuclear polarization （DNP） has become a very important hyperpolarization method because it can dramatically increase the sensitivity of nuclear magnetic resonance （NMR） of various molecules. Liquid-state DNP based on Overhauser effect is capable of directly enhancing polarization of all kinds of nuclei in the system. The combination of simultaneous Overhauser multi-nuclei enhancements with the multi-nuclei parallel acquisitions provides a variety of important applications in both MR spectroscopy （MRS） and image （MRI）. Here we present two simple illustrative examples for simultaneously enhanced multi-nuclear spectra and images to demonstrate the principle and superiority. We have observed very large simultaneous DNP enhancements for different nuclei, such as XH and 23Na, 1H and 31p, 19F and 31p, especially for the first time to report sodium ion enhancement in liquid. We have also obtained the simultaneous images of 19H and 31p, 19F and 31p at low field by solution-state DNP for the first time.展开更多
The collision processes of proton with H(1s) atoms, which is embedded in strong transverse magnetic fields perpendicular to the initial velocity of the projectile, are studied with the classical trajectory Monte Carlo...The collision processes of proton with H(1s) atoms, which is embedded in strong transverse magnetic fields perpendicular to the initial velocity of the projectile, are studied with the classical trajectory Monte Carlo method in the energy range 25 keV /u–2000 keV /u and B ～ 104 T. It is found that the charge exchange cross section is decreased while the ionization cross section is increased significantly. The physics of magnetic field effects is analyzed by the time evolution of electron energy and trajectories, and it is found that these effects are induced by the diamagnetic term in the interaction, continuum electron trapping in the target regions and the Lorentz force. The velocity distributions of the ionized electrons, significantly influenced by the applied fields, are also presented.展开更多
基金The project supported by National Natural Science Foundation of China under Grant No.10778719the Scientific Research Fund of the Education Department of Sichuan Province under Grant No.2006A079the Science and Technological Foundation of China West Normal University
文摘The electron capture of Gamow--Teller transition on iron group nuclei is investigated in a strong magnetic. field at the crusts of neutron stars. The results show that the magnetic field has only a slight effect on the electron capture rates with the range of the magnetic fields （10^9 - 10^13 G） on surfaces of most neutron stars, whereas for some magnetars whose range of the magnetic field is 10^13 - 10^18 G, the electron capture rates of most iron group nuclei would be debased greatly and may be even decreased overrun 3 orders of magnitude by the strong magnetic field.
基金supported by the Chinese Academy of Sciences(ZDYZ2010-2)the Ministry of Science and Technology of China (2011YQ120035)the National Natural Science Foundation of China (11405264,11274347,21221064,11575287)
文摘Dynamic nuclear polarization （DNP） has become a very important hyperpolarization method because it can dramatically increase the sensitivity of nuclear magnetic resonance （NMR） of various molecules. Liquid-state DNP based on Overhauser effect is capable of directly enhancing polarization of all kinds of nuclei in the system. The combination of simultaneous Overhauser multi-nuclei enhancements with the multi-nuclei parallel acquisitions provides a variety of important applications in both MR spectroscopy （MRS） and image （MRI）. Here we present two simple illustrative examples for simultaneously enhanced multi-nuclear spectra and images to demonstrate the principle and superiority. We have observed very large simultaneous DNP enhancements for different nuclei, such as XH and 23Na, 1H and 31p, 19F and 31p, especially for the first time to report sodium ion enhancement in liquid. We have also obtained the simultaneous images of 19H and 31p, 19F and 31p at low field by solution-state DNP for the first time.
基金Supported by National Natural Science Foundation of China under Grant Nos.11104017,11025417,11075023,10974021,10979007the Natoinal Basic Research Programm of China under Grant No.2013CB922200the Science and Technology Foundation of Chinese Academy of Engeering Physics under Grant No.2014B09036
文摘The collision processes of proton with H(1s) atoms, which is embedded in strong transverse magnetic fields perpendicular to the initial velocity of the projectile, are studied with the classical trajectory Monte Carlo method in the energy range 25 keV /u–2000 keV /u and B ～ 104 T. It is found that the charge exchange cross section is decreased while the ionization cross section is increased significantly. The physics of magnetic field effects is analyzed by the time evolution of electron energy and trajectories, and it is found that these effects are induced by the diamagnetic term in the interaction, continuum electron trapping in the target regions and the Lorentz force. The velocity distributions of the ionized electrons, significantly influenced by the applied fields, are also presented.
