A Theoretical Study on the Photochromic Mechanism of 1-Phenyl-3-methyl-4-（6-hydro-4-amino-5-sulfo-2,3-pyrazine）-pyrazole-5-one

The photochromic mechanism of 1-phenyl-3-methyl-4-（6-hydro-4-amino-5-sulfo-2,3- pyrazine）-pyrazole-5-one has been investigated using the density functional theory（DFT）. The solvent effect is simulated using the polarizable continuum model（PCM） of the self-consistent reaction field theory. According to the crystal structure of the title compound, an intramolecular proton transfer mechanism from enol to keto form was proposed to interpret its photochromism. Bader＇s atom-in-molecule（AIM） theory is used to investigate the nature of hydrogen bonds and ring structures. Time-dependent density functional theory（TDDFT） calculation results show that the photochromic process from enol to keto form is reasonable. The conformation and molecular orbital analysis of enol and keto forms explain why only intramolecular proton transfer is possible. The results from analyzing the energy and dipole moments of enol form, transition state and keto form in the gas phase and in different solvents have been used to assess the stability of the title compound.     

北斗实时卫星共视时间传递技术及其性能评估

全球导航卫星系统（Global Navigation Satellite System,GNSS）时间传递技术以其低成本、高精度、广覆盖范围等特点，广泛应用到高精度时频领域。传统卫星共视技术利用全球卫星导航时间比对标准（Common GNSS Generic Time Transfer Standard,CGGTTS）共视文件实现事后高精度时间传递，很难实现实时时间传递。为满足数字换流站、电力物联网、移动通信等对实时、高精度时间传递的需求，研究了基于北斗三号全球卫星导航定位系统（BDS-3）伪距观测数据的实时卫星共视技术，开展了短基线和西安-三亚长基线北斗实时卫星共视时间传递实验来评估实时共视时间传递性能。实验结果表明北斗实时卫星共视时间传递精度优于1 ns，可为时频系统、数字换流站等应用领域提供纳秒级时间同步和纳秒级时间溯源服务。