• 제목/요약/키워드: Picosecond

검색결과 116건 처리시간 0.024초

STUDY OF CONTACT ION PAIR DYNAMICS IN VIEW OF THE MOLECULAR SHAPES

  • Han, Chul-Hee
    • Journal of Photoscience
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    • 제3권3호
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    • pp.147-151
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    • 1996
  • Dynamics of contact ion-pair between 1, 2, 4, 5-tetracyanobenzene anion and cation of biphenyl derivatives was investigated on the picosecond time scale. Solvent effect on the electron transfer was observed and electron transfer rates were examined using Marcus equation which contains distance dependence of the electron transfer rate in the frequency factor, along with the consideration of molecular shape. From the discussion based on disk model for molecular shape, contribution of interring torsional motion of biphenyl to the inner-sphere reorganization energy is strongly suggested, which leads to the physical explanation for the observed solvent effect on the rate of electron transfer.

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Junction, Circuit and System Developments for a High-$T_c$ Superconductor Sampler

  • Hidaka, M.;Satoh, T.;Tahara, S.
    • Progress in Superconductivity
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    • 제1권2호
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    • pp.81-84
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    • 2000
  • A Josephson sampler circuit using high-Tc superconductor (HTS) ramp-edge junctions has been designed, fabricated, and experimentally tested. It consists of five ramp-edge junctions with a stacked groundplane and is based on single-flux-quantum (SFQ) operations. The sampler was used to measure current waveforms at picosecond and microampere resolutions. We are developing a system based on the sampler for measuring the current waveform in a room-temperature sample. And measuring current flowing through wiring in a semiconductor large-scale integrated circuit is a promising application for the HTS sampler system.

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극초단 펄스 레이저의 파장변환을 위한 이축 비선형 광학 결정에서 분산의 새로운 계산법 (A novel method for calculation of dispersions in biaxial crystals for frequency conversion of short pulse lasers)

  • Park Jae U;Yun Chun Seop
    • 한국광학회:학술대회논문집
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    • 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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    • pp.222-223
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    • 2003
  • As laser pulse width becomes shortened from nanoseconds to femtoseconds, the effects caused by the dispersions of nonlinear optical mediums, such as group velocity mismatch and group velocity dispersion become considerably significant. The group velocity mismatch and group velocity dispersion are the major factors that lead to a decrease of frequency conversion efficiency and pulse spreading for picosecond and femtosecond pulses. (omitted)

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피코초 레이저 펄스에 의한 백색광 발생 (White-light Continuum Generation by a picosecond laser pulse)

  • 강명균;이승묵;김도석;이범구
    • 한국광학회:학술대회논문집
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    • 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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    • pp.244-245
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    • 2001
  • 강한 펄스 레이저가 렌즈에 의해 투명한 매질 속에 집광되면 가시광선 영역에서부터 적외선 영역에 걸친 넓은 파장대의 빛이 발생하게 되는데 이것을 White-Light Continuum이라고 한다. 이 현상은 1970년에 Alfano 와 Shapiro에 의해 처음으로 발견되었으며 그 후에 여러 투명한 매질들을 통해 White-light continuum의 발생이 확인되었다. 물($H_2O$)과 중수(D$_2$O)에서도 이런 펄스 백색광의 발생이 관찰되어졌으며 고체 매질에 비해 집광된 강한 빛에 의해 생기는 손상에 대한 self-healing이 뛰어나 백색광을 발생시키기 위한 이상적인 매질로 인식도고 있다. (중략)

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BBO 결정을 이용한 Pico초 광매개 발생과 증폭 (Picosecond optical parametric generation and amplification using BBO crystals)

  • 유난이;최혜영;차명식
    • 한국광학회:학술대회논문집
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    • 한국광학회 2000년도 하계학술발표회
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    • pp.244-245
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    • 2000
  • 비선형광학 결정을 이용한 optical parametric generation(OPG)은 coherent tunable radiation을 얻는 방법으로 매우 효과적이다. Beta barium borate(BBO) 결정은 비선형성이 클 뿐만 아니라 광손상문턱이 높고 자외선에서부터 근 적외선영역까지(2 -0.2$mu extrm{m}$) 투명하여 optical parametric oscillation(OPO)이나 OPG/OPA(optical parametric generation/amplification)에 많이 활용되고 있다.[1-2] 분광학적 연구와 여러 가지 응용 측면에서 넓은 영역의 파장가변이 손쉽고 높은 에너지를 갖는 pico 초coherent source는 중요하며, 이는 결정의 비선형성을 이용하여 공진기를 구성하지 않고서도 OPG/OPA를 통하여 실현 가능하다. (중략)

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Study of rganized Assemblies and Surfaces Using Picosecond Lasers

  • Bhattacharyya, Kankan
    • Journal of Photoscience
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    • 제6권3호
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    • pp.123-128
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    • 1999
  • Dynamics of many ultrafast processes are markedly slowed down in various organized molecular assemblies compared to ordinary liquids. We will show that the solvation dynamics of water molecules is affected amost dramatically and is retarded by 3 ∼4 orders of magnitude in microemulsions, micells and lipids. We will also discuss how the access to fewer water molucules and the drastically altered local pH in an organized asembly affected the excited state proton transfer processes. Finally, we will show how surface second haromonic generation can be used to study the air-water surface.

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Picosecond Protein Fluorescence and Time-Resolved $Eu^{3+}$ Luminescence Spectroscopic Studies on the Roles of $Ca^{2+}$ in Subtilisin Carlsberg

  • Lee, Sunbae;Jang, Du-Jeon
    • 한국생물물리학회:학술대회논문집
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    • 한국생물물리학회 1997년도 학술발표회
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    • pp.44-44
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    • 1997
  • Ca$^{2+}$ is one of the most common metal ions associated with proteins, playing more or less well-defined functional roles in biological activities. In protease, the presence of $Ca^{2+}$ slows down autolysis and enhances thermal stability. Subtilisin, one of the best studied proteases, is known to have two $Ca^{2+}$ -binding sites.(omitted)

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