We have studied highly excited sodium in various electric fields,parallel electric and magnetic fields,with oneσandπphoton irradiation,and even in a magnetic field with a complex laser polarization configuration.The...We have studied highly excited sodium in various electric fields,parallel electric and magnetic fields,with oneσandπphoton irradiation,and even in a magnetic field with a complex laser polarization configuration.Theσspectra shows a simple linear Stark effect with the applied electric field,while theπspectra exhibits a strong non-linear dependence on the electric field.Theπtransitions in parallel fields show a similar behavior to that in a pure electric field but the spectra get more smooth due to the magnetic field.The diamagnetic spectrum with laser polarization angles between 0 andπ/2 proves that it can be reproduced by simple linear combination ofπandσcomponents,indicating there is no interference between theπandσchannels.A full quantum calculation considering the quantum defects accounts for all the observations.The quantum defects,especially for the channel np,play an important role in the spectral profile.展开更多
Based on the facts that multijunction solar cells can increase the efficiency and concentration can reduce the cost dramatically, a special design of parallel multijunction solar cells was presented. The design employ...Based on the facts that multijunction solar cells can increase the efficiency and concentration can reduce the cost dramatically, a special design of parallel multijunction solar cells was presented. The design employed a diffractive optical element(DOE) to split and concentrate the sunlight. A rainbow region and a zero-order diffraction region were generated on the output plane where solar cells with corresponding band gaps were placed. An analytical expression of the light intensity distribution on the output plane of the special DOE was deduced, and the limiting photovoltaic efficiency of such parallel multijunction solar cells was obtained based on Shockley–Queisser's theory. An efficiency exceeding the Shockley–Queisser limit(33%) can be expected using multijunction solar cells consisting of separately fabricated subcells.The results provide an important alternative approach to realize high photovoltaic efficiency without the need for expensive epitaxial technology widely used in tandem solar cells, thus stimulating the research and application of high efficiency and low cost solar cells.展开更多
The fragmentation pathways of two isomers of brassinosteroids,28-homobrassinolide(28-h-BL)and 28-epihomobrassinolide(28-eh-BL),have been investigated by tandem mass spectrometry(MSn,n=1,2,3,4)with the electrospray ion...The fragmentation pathways of two isomers of brassinosteroids,28-homobrassinolide(28-h-BL)and 28-epihomobrassinolide(28-eh-BL),have been investigated by tandem mass spectrometry(MSn,n=1,2,3,4)with the electrospray ionization(ESI) source.The ESI mass spectrometric fragmentation pathways of protonated 28-h-BL and 28-eh-BL were comprehensively elucidated,and the principles revealed in this investigation could potentially be used to identify and distinguish brassinosteroids and their isomers.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922003)the National Natural Science Foundation of China(Grant Nos.11174329 and 91121005)
文摘We have studied highly excited sodium in various electric fields,parallel electric and magnetic fields,with oneσandπphoton irradiation,and even in a magnetic field with a complex laser polarization configuration.Theσspectra shows a simple linear Stark effect with the applied electric field,while theπspectra exhibits a strong non-linear dependence on the electric field.Theπtransitions in parallel fields show a similar behavior to that in a pure electric field but the spectra get more smooth due to the magnetic field.The diamagnetic spectrum with laser polarization angles between 0 andπ/2 proves that it can be reproduced by simple linear combination ofπandσcomponents,indicating there is no interference between theπandσchannels.A full quantum calculation considering the quantum defects accounts for all the observations.The quantum defects,especially for the channel np,play an important role in the spectral profile.
基金supported by the National Natural Science Foundation of China(Grant Nos.91233202,21173260,and 51072221)the National Basic Research Program of China(Grant No.2012CB932903)
文摘Based on the facts that multijunction solar cells can increase the efficiency and concentration can reduce the cost dramatically, a special design of parallel multijunction solar cells was presented. The design employed a diffractive optical element(DOE) to split and concentrate the sunlight. A rainbow region and a zero-order diffraction region were generated on the output plane where solar cells with corresponding band gaps were placed. An analytical expression of the light intensity distribution on the output plane of the special DOE was deduced, and the limiting photovoltaic efficiency of such parallel multijunction solar cells was obtained based on Shockley–Queisser's theory. An efficiency exceeding the Shockley–Queisser limit(33%) can be expected using multijunction solar cells consisting of separately fabricated subcells.The results provide an important alternative approach to realize high photovoltaic efficiency without the need for expensive epitaxial technology widely used in tandem solar cells, thus stimulating the research and application of high efficiency and low cost solar cells.
基金supported by the National Natural Science Foundation of China(90717002 and 90717002)the Fundamental Research Funds for the Central Universitiesthe Project Sponsored by the Scientific Research Fundation for the Returned Overseas Chinese Scholars,Education Ministry of China
文摘The fragmentation pathways of two isomers of brassinosteroids,28-homobrassinolide(28-h-BL)and 28-epihomobrassinolide(28-eh-BL),have been investigated by tandem mass spectrometry(MSn,n=1,2,3,4)with the electrospray ionization(ESI) source.The ESI mass spectrometric fragmentation pathways of protonated 28-h-BL and 28-eh-BL were comprehensively elucidated,and the principles revealed in this investigation could potentially be used to identify and distinguish brassinosteroids and their isomers.
