分类： 物理学 >> 核物理学 提交时间： 2023-12-29
Dawei Si
Yan Zhou
Sheng Xiao
Zhi Qin
Dong Guo
Yuhao Qin
Yijie Wang
Boyuan Zhang
Baiting Tian
Zhigang Xiao
摘要： The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as asensitive probe to the short range correlation in atomic nuclei. The energy of the -rays can be measuredby collecting theˇCerenkov light in medium induced by the fast electrons generated in Compton scattering orelectromagnetic shower of the incident ray. Two types of detectors, based on pure water and lead glass asthe sensitive material respectively, are designed for the above purpose. The response and optical photonpropagation in detectors have been simulated based on the electromagnetic and optical processes in Geant4.The inherent energy resolution of 0.022(4) + 0.51(2)/E 1/2 for water and 0.0026(3) + 0.446(3)/E 1/2 forlead glass are obtained. The geometry size of lead glass and water are optimized at 30 30 30 cm3 and60 60 120 cm3 , respectively, for detecting high energy -rays at 160 MeV. Hough transform method hasbeen applied to reconstruct the direction of the incident -rays, giving the ability to distinguish experimentallythe high-energy rays produced in the reactions on the target from the random background cosmic ray muons.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cyanamide (NH2CN) and its isomer, carbodiimide (HNCNH), may form adenine in the interstellar medium (ISM) via a series of reactions. Therefore, they are considered key prebiotic molecules in the study of the origin of life. We used the three-phase NAUTILUS chemical code, which includes the gas, the dust surface, and the icy mantle, to investigate the formation and destruction of cyanamide and carbodiimide. We added over 200 new chemical reactions of the two isomers and related species, and established a relatively complete network. We applied cold core, hot corino/core and shock models to simulate the different physical environments, and found that the two isomers are mainly produced by the free radical reactions on grain surfaces. Our simulated results suggest that cyanamide and carbodiimide molecules come from surface chemistry at early evolutionary stages. Then they are released back to the gas phase, either by thermal process (in hot cores, hot corinos) or shock-induced desorption (in shock regions).We speculate that it is an inefficient route to form a tautomer of adenine by starting from molecules cyanoacetylene (C3NH), cyanamide and carbodiimide in ISM.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cyanamide (NH2CN) and its isomer, carbodiimide (HNCNH), may form adenine in the interstellar medium (ISM) via a series of reactions. Therefore, they are considered key prebiotic molecules in the study of the origin of life. We used the three-phase NAUTILUS chemical code, which includes the gas, the dust surface, and the icy mantle, to investigate the formation and destruction of cyanamide and carbodiimide. We added over 200 new chemical reactions of the two isomers and related species, and established a relatively complete network. We applied cold core, hot corino/core and shock models to simulate the different physical environments, and found that the two isomers are mainly produced by the free radical reactions on grain surfaces. Our simulated results suggest that cyanamide and carbodiimide molecules come from surface chemistry at early evolutionary stages. Then they are released back to the gas phase, either by thermal process (in hot cores, hot corinos) or shock-induced desorption (in shock regions).We speculate that it is an inefficient route to form a tautomer of adenine by starting from molecules cyanoacetylene (C3NH), cyanamide and carbodiimide in ISM.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yuansheng Tao
Fenghe Yang
Zihan Tao
Lin Chang
Haowen Shu
Ming Jin
Yan Zhou
Zhangfeng Ge
Xingjun Wang
摘要： Microwave photonics (MWP), harnessing the tremendous bandwidth of light to generate, process and measure wideband microwave signals, are poised to spark a new revolution for the information and communication fields. Within the past decade, new opportunity for MWP has emerged driven by the advances of integrated photonics. However, despite significant progress made in terms of integration level, a fully on-chip MWP functional system comprising all the necessary photonic and electronic components, is yet to be demonstrated. Here, we break the status quo and provide a complete on-chip solution for MWP system, by exploiting hybrid integration of indium phosphide, silicon photonics and complementary metal-oxide-semiconductor (CMOS) electronics platforms. Applying this hybrid integration methodology, a fully chip-based MWP microwave instantaneous frequency measurement (IFM) system is experimentally demonstrated. The unprecedented integration level brings great promotion to the compactness, reliability, and performances of the overall MWP IFM system, including a wide frequency measurement range (2-34 GHz), ultralow estimation errors (10.85 MHz) and a fast response speed (0.3 ns). Furthermore, we deploy the chip-scale MWP IFM system into realistic application tasks, where diverse microwave signals with rapid-varying frequencies at X-band (8-12 GHz) are accurately identified in real-time. This demonstration marks a milestone for the development of integrated MWP, by providing the technology basis for the miniaturization and massive implementations of various MWP functional systems.
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