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From Euler disk to phonon bottleneck effect: excited state physics

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The Innovation 2024年第3期5卷 7-8页

作者： Xinnian Lin Shaohua Fu Yanni Zhai Wenhui Wang Haochen Li Ruizhi Zhang Sheng Meng Jimin Zhao School of Physics Xi’an Jiaotong UniversityXi’an 710049China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China

The Euler disk,known since 1765,1 describes a solid disk that rotates on a smooth,firm surface,similar to a coin spun by a finger on a table,before its energy dissipates and it falls on the table.2 It represents a typical nonequilibrium excited state in classical physics.The most striking characteristic of an Euler disk is that it exhibits a sharply enhanced sound frequency when approaching the critical time,tc,after which the disk instantly ceases rotation and precession.At the excited-state-to-ground-state transition,its frequency abruptly changes from infinite to zero.This quasi-divergent and suddenly disappearing behavior is intriguing,revealing that this is a shared physical property in the microscopic quantum regime.

关键词： state excited sharply

Transient stimulated Raman scattering spectroscopy and imaging

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Light(Science & Applications) 2024年第4期13卷 654-663页

作者： Qiaozhi Yu Zhengjian Yao Jiaqi Zhou Wenhao Yu Chenjie Zhuang Yafeng Qi Hanqing Xiong National Biomedical Imaging Center College of Future TechnologyPeking UniversityBeijing 100871China Biomedical Engineering Department College of Future TechnologyPeking UniversityBeijing 100871China

Stimulated Raman scattering(SRS)has been developed as an essential quantitative contrast for chemical imaging in recent years.However,while spectral lines near the natural linewidth limit can be routinely achieved by state-of-the-art spontaneous Raman microscopes,spectral broadening is inevitable for current mainstream SRS imaging methods.This is because those SRS signals are all measured in the frequency domain.There is a compromise between sensitivity and spectral resolution:as the nonlinear process benefits from pulsed excitations,the fundamental time-energy uncertainty limits the spectral resolution.Besides,the spectral range and acquisition speed are mutually restricted.Here we report transient stimulated Raman scattering(T-SRS),an alternative time-domain strategy that bypasses all these fundamental conjugations.T-SRS is achieved by quantum coherence manipulation:we encode the vibrational oscillations in the stimulated Raman loss(SRL)signal by femtosecond pulse-pair sequence excited vibrational wave packet interference.The Raman spectrum was then achieved by Fourier transform of the time-domain SRL signal.Since all Raman modes are impulsively and simultaneously excited,T-SRS features the natural-linewidth-limit spectral line shapes,laser-bandwidth-determined spectral range,and improved sensitivity.With~150-fs laser pulses,we boost the sensitivity of typical Raman modes to the sub-mM level.With all-plane-mirror high-speed time-delay scanning,we further demonstrated hyperspectral SRS imaging of live-cell metabolism and high-density multiplexed imaging with the natural-linewidth-limit spectral resolution.T-SRS shall find valuable applications for advanced Raman imaging.

关键词： scattering excited mutually

Experimental and numerical study on atmospheric-pressure air dielectric barrier discharge via 50 Hz/5000 Hz dual-frequency excitation

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High Voltage 2024年第2期9卷 391-402页

作者： Junwen He Bangfa Peng Guanglin Yu Ronggang Wang Nan Jiang Jie Li Yan Wu School of Electrical Engineering Dalian University of TechnologyDalianChina Canmax Technologies Co. Ltd.SuzhouChina

A dual-frequency(DF)dielectric barrier discharge,excited by the superposition of a 50 Hz low frequency(LF)and a 5000 Hz intermediate frequency(IF),is proposed to enhance discharge.The effect of the LF voltage component on the breakdown behaviour of the DF discharge during different periods has been studied both experimentally and numerically.The number of high-current pulses rises as the LF voltage increases.The statistical analysis shows that the number of the current pulse amplitude above 80 mA in the DF discharge reaches nearly 6 times that in the IF discharge.Additionally,the total discharge energy in the DF discharge is significantly higher than that in the IF discharge.The simulation re-produces the temporal variation of the breakdown behaviours in the DF discharge.The simulated results reveal that the maximal electric field strength of the breakdown process is greater in the DF discharge compared to the IF discharge during a half-period of DF.Finally,the comparison between the IF and DF discharges exhibits that the LF voltage regulates the accumulation of residual charged species on the dielectric surface after the breakdown by modulating the residual voltage between the air gap.

关键词： dielectric excitation excited

Easy Tiger's Rocking Debut

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城市漫步（GBA版） 2024年第4期 13-15页

作者： Kirby John Carney 不详

We sit down with Easy Tiger's lead singer TC outside of The GOAT in Guangzhou's Panyu district.He is in a jolly and excited mood as he reminisces about the early days.

关键词： Easy outside excited

Enhanced blue-light excited cyan-emitting persistent luminescence of BaLu_(2)Al_(2)Ga_(2)SiO_(12)∶Ce3+,Bi3+phosphors for AC-LEDs via defect modulation

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Light(Science & Applications) 2022年第7期11卷 1542-1554页

作者： Weihong Yuan Ran Pang Shangwei Wang Tao Tan Chengyu Li Chaowei Wang Hongjie Zhang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China Hefei 230026China Zhongke Rare Earth(Guangzhou)Co. LtdGuangzhou 510700China

Alternating current light-emitting diodes(AC-LEDs)have received significant attention from both academia and industry due to their remarkable benefits of more compact volume,cheaper manufacturing cost,greater energy usage efficiency,and longer service life.One of the most significant challenges for AC-LEDs is the flicker effect,which is mainly caused by the unavoidable 5-20 ms dimming time.Aiming to reduce the flicker effect,we designed a series of excellent blue-light excited cyan-emitting persistent luminescence(PersL)phosphors BaLu_(2)Al_(2)Ga_(2)SiO_(12)∶Ce^(3+),Bi^(3+)via defect engineering of co-doping Bi^(3+).Interestingly,we found that co-doping Bi^(3+)not only effectively enhanced the PersL intensity,but also regulated the PersL lifetime of this phosphors.As the Bi^(3+)co-doping concentration increases to 0.01,the T80 value(the time when the PersL intensity decreases to 80%of the initial intensity)increases from 0.24 to 19.61 ms,which proves to be effective in compensating the flicker effect of AC-LEDs.A new method of generating white light emission during the dimming time through adding the blue-light excited cyan PersL phosphor to the original orange-red PersL phosphor was proposed and an AC-LED lamp with a decreased percent flicker of 48.15%was fabricated,which is significantly better than the other currently reported AC-LED devices based on PersL phosphors.These results demonstrate that BaLu_(2)Al_(2)Ga_(2)SiO_(12):Ce^(3+),Bi^(3+)might be an attractive material for low-flicker AC-LEDs.

关键词： excited luminescence defect

A molecular dynamics study of laser-excited gold

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Matter and Radiation at Extremes 2022年第3期7卷 20-30页

作者： Jacob M.Molina T.G.White University of Nevada RenoNevada 89557USA

The structural evolution of laser-excited systems of gold has previously been measured through ultrafast MeV electron diffraction.However,there has been a long-standing inability of atomistic simulations to provide a consistent picture of the melting process,leading to large discrepancies between the predicted threshold energy density for complete melting,as well as the transition between heterogeneous and homogeneous melting.We make use of two-temperature classical molecular dynamics simulations utilizing three highly successful interatomic potentials and reproduce electron diffraction data presented by Mo et al.[Science 360,1451–1455(2018)].We recreate the experimental electron diffraction data,employing both a constant and temperature-dependent electron–ion equilibration rate.In all cases,we are able to match time-resolved electron diffraction data,and find consistency between atomistic simulations and experiments,only by allowing laser energy to be transported away from the interaction region.This additional energy-loss pathway,which scales strongly with laser fluence,we attribute to hot electrons leaving the target on a timescale commensurate with melting。

关键词： diffraction. excited dynamics

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美文秀

英语角 2024年第10期 42-45页

New Year New Beginning The new school term is coming!I'm so excited to see all my friends again after the long break.Waving goodbye to lazy days and saying hello to early mornings might not be the most exciting thing。

关键词： break excited saying

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你我风采秀

英语角 2024年第17期 44-47页

最近,秋天姐姐收到了很多小朋友的来稿,这些作文都写得非常棒,一起来看看吧。Swimming Lesson Today was my first swimming lesson,and I was so excited.Mum signed me up(报名)for a swimming class because she said it was importa... 详细信息

关键词： really excited swimming

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Kindergarten Dad

China Weekly 2024年第1期 62-62页

作者： Sam Duckett 不详

My daughter recently completed her first year in kindergarten,which meant it was time for me to participate in my first parent-teacher conference.I was excited to find out how she was doing at school,and at the same time a little nervous.I had heard stories about what to expect at these kinds of events,but it's fair to say it was completely different from my expectations.In the UK parent-teacher conferences are often a great opportunity to have a one-to-one meeting with the school faculty and reflect on how your child is progressing.I recall my mum dreading these meetings,as I was apparently quite a handful.

关键词： garten daughter excited