We present a new method to identify the critical point for the Bose-Einstein condensation (BEC) of a trapped Bose gas. We calculate the momentum distribution of an interacting Bose gas near the critical temperature,...We present a new method to identify the critical point for the Bose-Einstein condensation (BEC) of a trapped Bose gas. We calculate the momentum distribution of an interacting Bose gas near the critical temperature, and find that it deviates significantly from the Gaussian profile as the temperature approaches the critical point. More importantly, the standard deviation between the calculated momentum spectrum and the Gaussian profile at the same temperature shows a turning point at the critical point, which can be used to determine the critical temperature. These predictions are also confirmed by our BEC experiment for magnetically trapped ST Rb gases.展开更多
The momentum profile of an aeolian saltation cloud is poorly understood. In this paper, height profiles for saltation momentum are reconstructed for three particle-size populations at four wind velocities based on pro...The momentum profile of an aeolian saltation cloud is poorly understood. In this paper, height profiles for saltation momentum are reconstructed for three particle-size populations at four wind velocities based on profiles for mean particle velocity and relative particle concentration of saltation cloud obtained using particle image velocimetry in a wind tunnel. The results suggest that the saltation momentum profiles are characterized by peak curves with a maximum at some height above the surface. The height of this maximum increases with increasing wind velocity, but decreases with increasing particle size. It is linearly correlated with average saltation height and is comparable with the results of numerical simulations in a previous study. Our results confirm that Bagnold’s kink is an important feature of wind velocity profiles modified by the presence of saltating particles and that the height of the kink is closely related to the average trajectories of the saltating particles.展开更多
The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy sp...The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution (e, 2e) electron momentum spectrometer (EMS) at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field (SCF) theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11104322the National Key Basic Research and Development Program of China under Grant No 2011CB921503
文摘We present a new method to identify the critical point for the Bose-Einstein condensation (BEC) of a trapped Bose gas. We calculate the momentum distribution of an interacting Bose gas near the critical temperature, and find that it deviates significantly from the Gaussian profile as the temperature approaches the critical point. More importantly, the standard deviation between the calculated momentum spectrum and the Gaussian profile at the same temperature shows a turning point at the critical point, which can be used to determine the critical temperature. These predictions are also confirmed by our BEC experiment for magnetically trapped ST Rb gases.
基金the funding from the Natural Science Foundation of China (40638038)the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX3-YW-329)
文摘The momentum profile of an aeolian saltation cloud is poorly understood. In this paper, height profiles for saltation momentum are reconstructed for three particle-size populations at four wind velocities based on profiles for mean particle velocity and relative particle concentration of saltation cloud obtained using particle image velocimetry in a wind tunnel. The results suggest that the saltation momentum profiles are characterized by peak curves with a maximum at some height above the surface. The height of this maximum increases with increasing wind velocity, but decreases with increasing particle size. It is linearly correlated with average saltation height and is comparable with the results of numerical simulations in a previous study. Our results confirm that Bagnold’s kink is an important feature of wind velocity profiles modified by the presence of saltating particles and that the height of the kink is closely related to the average trajectories of the saltating particles.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 19854002, 19774037 and 10274040) and the Research Fund for the Doctoral Program Foundation of Institution of Higher Education of China (Grant No 1999000327).
文摘The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution (e, 2e) electron momentum spectrometer (EMS) at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field (SCF) theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.