Investigation on vibrational excitation and relaxation process will provide important in- formation for a better understanding of ultrafast dynamic response of energetic materials. Using sub-ps time-resolved coherent ...Investigation on vibrational excitation and relaxation process will provide important in- formation for a better understanding of ultrafast dynamic response of energetic materials. Using sub-ps time-resolved coherent anti-Stokes Raman scattering （CARS） experiments, we directly observe excitation of vibrational mode vs（NO2） and its relaxation process of ground state HNS （2,2＇,4,4＇,6,6＇-hexanitrostillbenein） in solution. The results show that vs（NO2） at 1385 cm-1 has been excited and relaxation time of 0.38 and 8.5 ps is obtained. The possible quantum beat frequencies are also discussed via fs-CARS experiments. The original results provide an insight into ultrafast process of energetic materials.展开更多
From the beginnings of Wahabism in the 18th century to the so called Islamic State of Iraq and the Levant （ISIL, ISIS） violence has occasionally been justified in the name of Islam, which is problematic for secular ...From the beginnings of Wahabism in the 18th century to the so called Islamic State of Iraq and the Levant （ISIL, ISIS） violence has occasionally been justified in the name of Islam, which is problematic for secular and traditional scholars alike. This paper demonstrates that there are three complex, interrelated causes for this violence： foreign military intervention, Salafi-Jihadism and a utopian state founded upon faith and justice, i.e. a caliphate.展开更多
Thomas-Fermi theory is an approximate method, which is widely used to describe the properties of matter at various hierarchical levels （atomic nucleus, atom, molecule, solid, etc.）. Special development is achieved u...Thomas-Fermi theory is an approximate method, which is widely used to describe the properties of matter at various hierarchical levels （atomic nucleus, atom, molecule, solid, etc.）. Special development is achieved using Thomas-Fermi theory to the theory of extreme states of matter appearing under high pressures, high temperatures or strong external fields. Relevant sections of physics and related sciences （astrophysics, quantum chemistry, a number of applied sciences） determine the scope of Thomas-Fermi theory. Popularity Thomas-Fermi theory is related to its relative simplicity, clarity and versatility. The latter means that result of the calculation by Thomas-Fermi theory applies immediately to all chemical elements： the transition from element to element is as simple scale transformation. These features make it highly convenient tool for qualitative and, in many cases, quantitative analysis.展开更多
A recently developed time-resolved coherent anti-Stokes Raman scattering(tr-CARS) technique allows the measurement of vibrational coherences with high frequency differences with the ambient environment.The method is b...A recently developed time-resolved coherent anti-Stokes Raman scattering(tr-CARS) technique allows the measurement of vibrational coherences with high frequency differences with the ambient environment.The method is based on the short spatial extension of femtosecond pulses with a broadband tunable nonlinear optical parametric amplifier(NOPA) and an internal time delay between the probe and pump/Stokes pulse pair in the CARS process.The different beat frequencies between Raman modes can be selectively detected as oscillations in the tr-CARS transient signal with the broadband tunable NOPA.In this work,we aim at the Raman C-H stretching vibrations from 2800 cm 1 to 3000 cm 1,within which the different vibrational modes in both ethanol and methanol are selectively excited and simultaneously detected.The high time resolution of the experimental set-up allows one to monitor the vibrational coherence dynamics and to observe the quantum beat phenomena on a terahertz scale.This investigation indicates that the femtosecond tr-CARS technique is a powerful tool for the real-time monitoring and detection of molecular and biological agents,including airborne contaminants such as bacterial spores,viruses and their toxins.展开更多
文摘Investigation on vibrational excitation and relaxation process will provide important in- formation for a better understanding of ultrafast dynamic response of energetic materials. Using sub-ps time-resolved coherent anti-Stokes Raman scattering （CARS） experiments, we directly observe excitation of vibrational mode vs（NO2） and its relaxation process of ground state HNS （2,2＇,4,4＇,6,6＇-hexanitrostillbenein） in solution. The results show that vs（NO2） at 1385 cm-1 has been excited and relaxation time of 0.38 and 8.5 ps is obtained. The possible quantum beat frequencies are also discussed via fs-CARS experiments. The original results provide an insight into ultrafast process of energetic materials.
文摘From the beginnings of Wahabism in the 18th century to the so called Islamic State of Iraq and the Levant （ISIL, ISIS） violence has occasionally been justified in the name of Islam, which is problematic for secular and traditional scholars alike. This paper demonstrates that there are three complex, interrelated causes for this violence： foreign military intervention, Salafi-Jihadism and a utopian state founded upon faith and justice, i.e. a caliphate.
文摘Thomas-Fermi theory is an approximate method, which is widely used to describe the properties of matter at various hierarchical levels （atomic nucleus, atom, molecule, solid, etc.）. Special development is achieved using Thomas-Fermi theory to the theory of extreme states of matter appearing under high pressures, high temperatures or strong external fields. Relevant sections of physics and related sciences （astrophysics, quantum chemistry, a number of applied sciences） determine the scope of Thomas-Fermi theory. Popularity Thomas-Fermi theory is related to its relative simplicity, clarity and versatility. The latter means that result of the calculation by Thomas-Fermi theory applies immediately to all chemical elements： the transition from element to element is as simple scale transformation. These features make it highly convenient tool for qualitative and, in many cases, quantitative analysis.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60878018 and 61008023)the Program of Excellentat Harbin Institute of Technology
文摘A recently developed time-resolved coherent anti-Stokes Raman scattering(tr-CARS) technique allows the measurement of vibrational coherences with high frequency differences with the ambient environment.The method is based on the short spatial extension of femtosecond pulses with a broadband tunable nonlinear optical parametric amplifier(NOPA) and an internal time delay between the probe and pump/Stokes pulse pair in the CARS process.The different beat frequencies between Raman modes can be selectively detected as oscillations in the tr-CARS transient signal with the broadband tunable NOPA.In this work,we aim at the Raman C-H stretching vibrations from 2800 cm 1 to 3000 cm 1,within which the different vibrational modes in both ethanol and methanol are selectively excited and simultaneously detected.The high time resolution of the experimental set-up allows one to monitor the vibrational coherence dynamics and to observe the quantum beat phenomena on a terahertz scale.This investigation indicates that the femtosecond tr-CARS technique is a powerful tool for the real-time monitoring and detection of molecular and biological agents,including airborne contaminants such as bacterial spores,viruses and their toxins.
