A high speed LIGBT with localized lifetime control by using high dose and low en ergy helium implantation(LC-LIGBT) is proposed.Compared with conventional LIGB Ts,particle irradiation results show that trade-off relat...A high speed LIGBT with localized lifetime control by using high dose and low en ergy helium implantation(LC-LIGBT) is proposed.Compared with conventional LIGB Ts,particle irradiation results show that trade-off relationship between turn- off time and forward voltage drop is improved.At the same time,the forward volta ge drop and turn-off time of such device are researched,when localized lifetime control region place near the p+-n junction,even in p+ anode.The results s how for the first time,helium ions,which stop in the p+ anode,also contribute to the forward voltage drop increasing and turn-off time reducing.展开更多
[Objective] This study aimed to identify the ultra-drying method most suitable for the storage of Chinese chive seeds through comparing different ultra-drying meth- ods. [Method] Through setting treatments including f...[Objective] This study aimed to identify the ultra-drying method most suitable for the storage of Chinese chive seeds through comparing different ultra-drying meth- ods. [Method] Through setting treatments including freezing, silica gel drying and heating drying at 50℃ as well as two controls, the effects of different drying methods for storing ultra-dried Chinese chive seeds were compared. [Result] There were no significant differences in the germination rate and seedling length between Chinese chive seeds treated with heating drying at 50℃ and those treated with either freezing or get drying at the initial stage of the storage. Storing of Chinese chive seeds previously treated with either heating drying at 50℃, or freezing or gel drying for 0-98 months at 20℃ hadn't caused any adverse effect on the germination rate of seeds. And the effect of different storage conditions on seedling length displayed earlier than that on the germination rate. There was no significant difference on seedling length between seeds treated with heating drying at 50℃ and those treated with freezing drying after stored for as long as 98 months, revealing similar efficacy on storing seeds. [Conclusion] Freezing drying requires huge investment and cost for perennial running, and silica gel drying is slow in drying and time-consuming. By contrast, heating drying at 50℃ is an economic and simple method, which can enable the Chinese chive seeds to sustain a longevity of eight years or more.展开更多
The reverse snapback phenomena (RSP) on I-V characteristics of static induction thyristors (SITH) are physically researched. The I-V curves of the power SITH exhibit reverse snapback phenomena, and even turn to th...The reverse snapback phenomena (RSP) on I-V characteristics of static induction thyristors (SITH) are physically researched. The I-V curves of the power SITH exhibit reverse snapback phenomena, and even turn to the conducting-state,when the anode voltage in the forward blocking-state is increased to a critical value. The RSP I-V characteristics of the power SITH are analyzed in terms of operating mechanism, double carrier injection effect, space charge effect, electron-hole plasma in the channel, and the variation in carrier lifetime. The reverse snapback mechanism is theoretically pro- posed and the mathematical expressions to calculate the voltage and current values at the snapback point are presented. The computing results are compared with the experiment values.展开更多
The precipitation and gettering behaviors of copper (Cu) at different defective regions in multicrystalline silicon were investigated by combining scanning infrared microscopy, optical microscopy, inductively couple...The precipitation and gettering behaviors of copper (Cu) at different defective regions in multicrystalline silicon were investigated by combining scanning infrared microscopy, optical microscopy, inductively coupled plasma mass spectrometry and microwave photo-conductance decay. It is found that the behaviors of Cu precipitation are strongly dependent on the defect density. Most of the Cu contaminants tend to form precipitates homogeneously in the low density defect region, while they mostly segregate at the defects and form precipitates heterogeneously in the high density defect region. In the case of heavy contamination, the Cu precipitate can significantly reduce the carrier lifetime of multicrystalline silicon due to their Schottkydiode behavior in the silicon substrate. A 900 °C rap thermal process (RTP) phosphorus gettering anneal cannot be sufficiently effective to remove the Cu precipitates in these two regions.展开更多
According to different mechanisms of dormancy,seeds of Gagea nigra L.Z.Shue were treated with different methods so as to investigate the effects of different treatments on seed germination of G.nigra.The results showe...According to different mechanisms of dormancy,seeds of Gagea nigra L.Z.Shue were treated with different methods so as to investigate the effects of different treatments on seed germination of G.nigra.The results showed that at 4 ℃,the seeds of G.nigra began to germinate on day 32 with germination period of 80 d and germination rate of 72%;room temperature(25 ℃) and acid and alkali treatments were all unsuitable for the germination of G.nigra seeds;no significant differences were found in germination rate of G.nigra seeds among warm water(50℃),ultrasound and 200 mg/L GA_3treatments(P 0.05);seed coat-removing treatment effectively promoted the germination of G.nigra seeds(P =0.002 0.01) with germination rate of 88%;seed coat piercing + 200 mg/L GA_3 and 500 mg/L GA_3+15% H_2O_2 treatments effectively promoted the germination of G.nigra seeds with germination rates of 84% and 82%,respectively(P0.05);the germination vigor of G.nigra seeds in the seed coat piercing + 200 mg/L GA_3 treatment was highest,and it was significantly higher than those in the other treatments.展开更多
A polytetrafluoroethylene (PTFE)-doped PbO2 electrode on a Ti substrate was prepared by galvanostatic method from the sulfamic acid bath (Ti/PTFE-F-PbO2-I) or nitric acid bath (Ti/PTFE-F-PbO2-II). Scanning Elect...A polytetrafluoroethylene (PTFE)-doped PbO2 electrode on a Ti substrate was prepared by galvanostatic method from the sulfamic acid bath (Ti/PTFE-F-PbO2-I) or nitric acid bath (Ti/PTFE-F-PbO2-II). Scanning Electron Microscopy revealed that the Ti/PTFE-PbO2-I electrode had a more regular morphology with smaller size crystals than the Ti/PTFE-F-PbO2-II electrode. On the basis of the results of both the accelerated electrolysis test and the empirical formula for estimating the service life of an electrode, the service life of the Ti/PTFE-PbO2-I electrode was predicted to be more than 7 years under conventional electrolysis conditions (0.1 A·cm^-2). During the treatment of 4-chlorophenol-contaminated water, the Ti/PTFE-PbO2-I anode showed both a good electro-catalytic activity and high electrochemical stability, exhibiting an excellent potential application.展开更多
The α-decay half-lives of a set of superheavy nuclear isotope chain from Z = 105 to 120 have been analyzed systematically within the WKB method, and some nuclear structure features are found. The decay barriers have ...The α-decay half-lives of a set of superheavy nuclear isotope chain from Z = 105 to 120 have been analyzed systematically within the WKB method, and some nuclear structure features are found. The decay barriers have been determined in the quasi-molecular shape path within the Generalized Liquid Drop Model (GLDM) including the proximity effects between nucleons in a neck and the mass and charge asymmetry. The results are in reasonable agreement with the published experimental data for the alpha decay half-llves of isotopes of charge 112, 114, and 116, of the element 294118 and of some decay products. A comparison of present calculations with the results by the DDM3Y effective interaction and by the Viola-Seaborg-Sobiczewski (VSS) formulae is also made. The experimental a decay half lives all stand in between the GLDM calculations and VSS formula results. This demonstrates the possibility of these models to provide reasonable estimates for the half-lives of nuclear decays by a emissions for the domain of SHN. The half-lives of these new nuclei are thus well tested from the reasonable consistence of the macroscopic, the microscopic, the empirical formulae and the experimental data. This also shows that the present data of SHN themselves are consistent. It could suggest that the present experimental claims on the existence of new elements Z =110 - 118 are reliable. It is expected that greater deviations of a few SHN between the data and the model may be eliminated by further improvements on the precision of the measurements.展开更多
During sexual reproduction of seaweeds, spermatozoid (sperm) discharge is triggered by chemical messengers (pheromones) released by the female gametes. The chemotactic ability of the sperm ensures fertilization succes...During sexual reproduction of seaweeds, spermatozoid (sperm) discharge is triggered by chemical messengers (pheromones) released by the female gametes. The chemotactic ability of the sperm ensures fertilization success. Using unialgal male and female gametophyte material under designated standard gametogenesis testing (SGT) conditions, the potential life-span of the sperm of two seaweeds, Saccharina japonica and Undaria pinnatifida, was assessed by their ability to fertilize eggs. Results show that within 20-30 min after being discharged, sperm of both species could complete fertilization without an apparent decline in fertilization rate. Although fertilization rate 60-120 min after sperm discharge dropped significantly in both species, some sperm were viable enough to fertilize the eggs. In S.japonica, at 12°C, some sperm were able to fertilize eggs up to 12 h after discharge. In both species, egg discharge rates (EDR) in the male and female mixed positive controls were significantly higher than those of all the sperm-testing groups. Doubling the seeded male gametophytes of S. japonica in the SGT tests significantly increased the EDR, further confirming the effect of the presence of the male on the female in terms of facilitating egg discharge from oogonia.展开更多
The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reactio...The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reaction affect the durability and cost of PEMFCs.Most previous reports on Pt-based electrocatalyst designs have focused more on improving their activity;however,with the commercialization of PEMFCs,durability has received increasing attention.In-depth insight into the structural evolution of Pt-based electrocatalysts throughout their lifecycle can contribute to further optimization of their activity and durability.The development of in situ electron microscopy and other in situ techniques has promoted the elucidation of the evolution mechanism.This mini review highlights recent advances in the structural evolution of Pt-based electrocatalysts.The mechanisms are adequately discussed,and some methods to inhibit or exploit the structural evolution of the catalysts are also briefly reviewed.展开更多
We in terms of optical theorem estimate the lifetime of B<SUB>c</SUB> meson with the parameters which are determined by fitting the data for the lifetimes and inclusive semileptonic decays of various B and...We in terms of optical theorem estimate the lifetime of B<SUB>c</SUB> meson with the parameters which are determined by fitting the data for the lifetimes and inclusive semileptonic decays of various B and D mesons. In the estimation, we find that the bound-state effects are important, and take them into account carefully in the framework which attributes the effects to the effective masses of the decay heavy quarks in the inclusive processes. We also find that to B<SUB>c</SUB> lifetime the penguin contribution is enhanced due to possible interference between the penguin and the 'tree part' c<SUB>1</SUB>O<SUB>1</SUB> + c<SUB>2</SUB>O<SUB>2</SUB>.展开更多
In this work, we evaluate the lifetimes of the doubly charmed baryons Ξcc^+ ,Ξcc^++, and Ωcc^+. We carefully calculate the non-spectator contributions at the quark level, where the Cabibbo-suppressed diagrams a...In this work, we evaluate the lifetimes of the doubly charmed baryons Ξcc^+ ,Ξcc^++, and Ωcc^+. We carefully calculate the non-spectator contributions at the quark level, where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment. If more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored.展开更多
As a key factor leading to the pressure-dependent R1-line-shift reversal and R1-state lifetime, at 10 K, the pressure-dependent variation of mixing-degree of |t2^2(^3T1)e^4T2) and |t2^32E〉 base-wavefunetions in ...As a key factor leading to the pressure-dependent R1-line-shift reversal and R1-state lifetime, at 10 K, the pressure-dependent variation of mixing-degree of |t2^2(^3T1)e^4T2) and |t2^32E〉 base-wavefunetions in the wavefunction of R1 state of LLGG:Cr^3+ has been calculated and analyzed. From this, the physical origin of the pressure-dependent R1-line-shift reversal has been revealed. Furthermore, by using the pressure-dependent values of the sum of all square mixlng-coefficients of |t2^2 (^3T1)e^4T2〉 in the wavefunction of R1 state, the lifetimes of R1 state of LLG G:Cr^3+ at various pressures have been calculat, ed, which arc in good agreement with observed results. The quantum anticrossing effect between t2^32E and t2^2 (^3T1)e^4T2 levels due to both spin-orbital interaction and electron-phonon interaction is remarkable, which is related to the admixture of |t2^2(^3T1)e^4T2) and |t2^32E〉 as well as the low high crystal-field transition.展开更多
Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential e...Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons (electron-hole pairs) but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems (e.g., semiconductor nanocrystals), multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions (an exciton plus an additional charge), and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The type- II band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is -2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-II nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.展开更多
文摘A high speed LIGBT with localized lifetime control by using high dose and low en ergy helium implantation(LC-LIGBT) is proposed.Compared with conventional LIGB Ts,particle irradiation results show that trade-off relationship between turn- off time and forward voltage drop is improved.At the same time,the forward volta ge drop and turn-off time of such device are researched,when localized lifetime control region place near the p+-n junction,even in p+ anode.The results s how for the first time,helium ions,which stop in the p+ anode,also contribute to the forward voltage drop increasing and turn-off time reducing.
基金Supported by the Major Research Program of Beijing Municipal Commission of Science and Technology(D131100000413001)the Beijing Nova Program(2008B37)+1 种基金National Key Technologies R&D Program(2012BAK26B03)the Special Fund for Construction of Scientific and Technological Innovation Ability of Beijing Academy of Agriculture and Forestry Sciences~~
文摘[Objective] This study aimed to identify the ultra-drying method most suitable for the storage of Chinese chive seeds through comparing different ultra-drying meth- ods. [Method] Through setting treatments including freezing, silica gel drying and heating drying at 50℃ as well as two controls, the effects of different drying methods for storing ultra-dried Chinese chive seeds were compared. [Result] There were no significant differences in the germination rate and seedling length between Chinese chive seeds treated with heating drying at 50℃ and those treated with either freezing or get drying at the initial stage of the storage. Storing of Chinese chive seeds previously treated with either heating drying at 50℃, or freezing or gel drying for 0-98 months at 20℃ hadn't caused any adverse effect on the germination rate of seeds. And the effect of different storage conditions on seedling length displayed earlier than that on the germination rate. There was no significant difference on seedling length between seeds treated with heating drying at 50℃ and those treated with freezing drying after stored for as long as 98 months, revealing similar efficacy on storing seeds. [Conclusion] Freezing drying requires huge investment and cost for perennial running, and silica gel drying is slow in drying and time-consuming. By contrast, heating drying at 50℃ is an economic and simple method, which can enable the Chinese chive seeds to sustain a longevity of eight years or more.
文摘The reverse snapback phenomena (RSP) on I-V characteristics of static induction thyristors (SITH) are physically researched. The I-V curves of the power SITH exhibit reverse snapback phenomena, and even turn to the conducting-state,when the anode voltage in the forward blocking-state is increased to a critical value. The RSP I-V characteristics of the power SITH are analyzed in terms of operating mechanism, double carrier injection effect, space charge effect, electron-hole plasma in the channel, and the variation in carrier lifetime. The reverse snapback mechanism is theoretically pro- posed and the mathematical expressions to calculate the voltage and current values at the snapback point are presented. The computing results are compared with the experiment values.
基金Projects (60906002, 50832006) supported by the National Natural Science Foundation of ChinaProject (2009QNA4007) supported by the Fundamental Research Funds for the Central Universities, China
文摘The precipitation and gettering behaviors of copper (Cu) at different defective regions in multicrystalline silicon were investigated by combining scanning infrared microscopy, optical microscopy, inductively coupled plasma mass spectrometry and microwave photo-conductance decay. It is found that the behaviors of Cu precipitation are strongly dependent on the defect density. Most of the Cu contaminants tend to form precipitates homogeneously in the low density defect region, while they mostly segregate at the defects and form precipitates heterogeneously in the high density defect region. In the case of heavy contamination, the Cu precipitate can significantly reduce the carrier lifetime of multicrystalline silicon due to their Schottkydiode behavior in the silicon substrate. A 900 °C rap thermal process (RTP) phosphorus gettering anneal cannot be sufficiently effective to remove the Cu precipitates in these two regions.
文摘According to different mechanisms of dormancy,seeds of Gagea nigra L.Z.Shue were treated with different methods so as to investigate the effects of different treatments on seed germination of G.nigra.The results showed that at 4 ℃,the seeds of G.nigra began to germinate on day 32 with germination period of 80 d and germination rate of 72%;room temperature(25 ℃) and acid and alkali treatments were all unsuitable for the germination of G.nigra seeds;no significant differences were found in germination rate of G.nigra seeds among warm water(50℃),ultrasound and 200 mg/L GA_3treatments(P 0.05);seed coat-removing treatment effectively promoted the germination of G.nigra seeds(P =0.002 0.01) with germination rate of 88%;seed coat piercing + 200 mg/L GA_3 and 500 mg/L GA_3+15% H_2O_2 treatments effectively promoted the germination of G.nigra seeds with germination rates of 84% and 82%,respectively(P0.05);the germination vigor of G.nigra seeds in the seed coat piercing + 200 mg/L GA_3 treatment was highest,and it was significantly higher than those in the other treatments.
基金Supported by the National Natural Science Foundation of China (20406019, 20876151)
文摘A polytetrafluoroethylene (PTFE)-doped PbO2 electrode on a Ti substrate was prepared by galvanostatic method from the sulfamic acid bath (Ti/PTFE-F-PbO2-I) or nitric acid bath (Ti/PTFE-F-PbO2-II). Scanning Electron Microscopy revealed that the Ti/PTFE-PbO2-I electrode had a more regular morphology with smaller size crystals than the Ti/PTFE-F-PbO2-II electrode. On the basis of the results of both the accelerated electrolysis test and the empirical formula for estimating the service life of an electrode, the service life of the Ti/PTFE-PbO2-I electrode was predicted to be more than 7 years under conventional electrolysis conditions (0.1 A·cm^-2). During the treatment of 4-chlorophenol-contaminated water, the Ti/PTFE-PbO2-I anode showed both a good electro-catalytic activity and high electrochemical stability, exhibiting an excellent potential application.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10505016 and 10575119, the Knowledge Innovation Project of the Chinese Academy of Sciences under Grant Nos. KJCX2-SW-N17, KJCX.SYW.N02, Major State Basic Research Development Program under Graalt No. 2007CB815000, and the Financial Support from DFG of Germany tCorresponding author,
文摘The α-decay half-lives of a set of superheavy nuclear isotope chain from Z = 105 to 120 have been analyzed systematically within the WKB method, and some nuclear structure features are found. The decay barriers have been determined in the quasi-molecular shape path within the Generalized Liquid Drop Model (GLDM) including the proximity effects between nucleons in a neck and the mass and charge asymmetry. The results are in reasonable agreement with the published experimental data for the alpha decay half-llves of isotopes of charge 112, 114, and 116, of the element 294118 and of some decay products. A comparison of present calculations with the results by the DDM3Y effective interaction and by the Viola-Seaborg-Sobiczewski (VSS) formulae is also made. The experimental a decay half lives all stand in between the GLDM calculations and VSS formula results. This demonstrates the possibility of these models to provide reasonable estimates for the half-lives of nuclear decays by a emissions for the domain of SHN. The half-lives of these new nuclei are thus well tested from the reasonable consistence of the macroscopic, the microscopic, the empirical formulae and the experimental data. This also shows that the present data of SHN themselves are consistent. It could suggest that the present experimental claims on the existence of new elements Z =110 - 118 are reliable. It is expected that greater deviations of a few SHN between the data and the model may be eliminated by further improvements on the precision of the measurements.
基金Supported by National High Technology Research and Development Program of China (863 Program)(No.2012AA10A413)the National Natural Science Foundation of China (Nos.41206146,41176135,41206142)+3 种基金the National Special Research Fund for Non-Profit Sector (Agriculture) from the Ministry of Agriculture (No.200903030)the Knowledge Innovation Program of Chinese Academy of Sciences (No.KSCX2-EW-B-3)the National Key Basic Program of Science and Technology-Platforms of Aquaculture Stock Resourcesthe Leading Academic Discipline Project of the Shanghai Municipal Education Commission (No.J50701)
文摘During sexual reproduction of seaweeds, spermatozoid (sperm) discharge is triggered by chemical messengers (pheromones) released by the female gametes. The chemotactic ability of the sperm ensures fertilization success. Using unialgal male and female gametophyte material under designated standard gametogenesis testing (SGT) conditions, the potential life-span of the sperm of two seaweeds, Saccharina japonica and Undaria pinnatifida, was assessed by their ability to fertilize eggs. Results show that within 20-30 min after being discharged, sperm of both species could complete fertilization without an apparent decline in fertilization rate. Although fertilization rate 60-120 min after sperm discharge dropped significantly in both species, some sperm were viable enough to fertilize the eggs. In S.japonica, at 12°C, some sperm were able to fertilize eggs up to 12 h after discharge. In both species, egg discharge rates (EDR) in the male and female mixed positive controls were significantly higher than those of all the sperm-testing groups. Doubling the seeded male gametophytes of S. japonica in the SGT tests significantly increased the EDR, further confirming the effect of the presence of the male on the female in terms of facilitating egg discharge from oogonia.
文摘The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reaction affect the durability and cost of PEMFCs.Most previous reports on Pt-based electrocatalyst designs have focused more on improving their activity;however,with the commercialization of PEMFCs,durability has received increasing attention.In-depth insight into the structural evolution of Pt-based electrocatalysts throughout their lifecycle can contribute to further optimization of their activity and durability.The development of in situ electron microscopy and other in situ techniques has promoted the elucidation of the evolution mechanism.This mini review highlights recent advances in the structural evolution of Pt-based electrocatalysts.The mechanisms are adequately discussed,and some methods to inhibit or exploit the structural evolution of the catalysts are also briefly reviewed.
文摘We in terms of optical theorem estimate the lifetime of B<SUB>c</SUB> meson with the parameters which are determined by fitting the data for the lifetimes and inclusive semileptonic decays of various B and D mesons. In the estimation, we find that the bound-state effects are important, and take them into account carefully in the framework which attributes the effects to the effective masses of the decay heavy quarks in the inclusive processes. We also find that to B<SUB>c</SUB> lifetime the penguin contribution is enhanced due to possible interference between the penguin and the 'tree part' c<SUB>1</SUB>O<SUB>1</SUB> + c<SUB>2</SUB>O<SUB>2</SUB>.
基金The project supported by National Natural Science Foundation of China
文摘In this work, we evaluate the lifetimes of the doubly charmed baryons Ξcc^+ ,Ξcc^++, and Ωcc^+. We carefully calculate the non-spectator contributions at the quark level, where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment. If more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored.
文摘As a key factor leading to the pressure-dependent R1-line-shift reversal and R1-state lifetime, at 10 K, the pressure-dependent variation of mixing-degree of |t2^2(^3T1)e^4T2) and |t2^32E〉 base-wavefunetions in the wavefunction of R1 state of LLGG:Cr^3+ has been calculated and analyzed. From this, the physical origin of the pressure-dependent R1-line-shift reversal has been revealed. Furthermore, by using the pressure-dependent values of the sum of all square mixlng-coefficients of |t2^2 (^3T1)e^4T2〉 in the wavefunction of R1 state, the lifetimes of R1 state of LLG G:Cr^3+ at various pressures have been calculat, ed, which arc in good agreement with observed results. The quantum anticrossing effect between t2^32E and t2^2 (^3T1)e^4T2 levels due to both spin-orbital interaction and electron-phonon interaction is remarkable, which is related to the admixture of |t2^2(^3T1)e^4T2) and |t2^32E〉 as well as the low high crystal-field transition.
文摘Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons (electron-hole pairs) but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems (e.g., semiconductor nanocrystals), multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions (an exciton plus an additional charge), and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The type- II band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is -2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-II nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.