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171.
利用相干受激Raman抽运,选择性地激发C2H2分子(X~1Σg v2=1,J")单一振转态.在Ra-man泵浦与探测激光不同偏振条件下,获得紫外探测激光诱导的A1Au(v3=1)-(X~1Σg v2=1,J")荧光增益光谱,从而研究了C2H2分子单一振转态的光学ACStark效应和mj的定向分布A0(1),利用stark线型加宽数值模型,从理论上计算得到的Rarnan线型与实验结果进行比较,二者符合程度相当好. 相似文献
172.
We describe a diode-pumped master-oscillator power-amplifier system with two-rod Nd:YAG media and double-stage relay optics scheme. At the repetition rate of 2.4 kHz it delivers an average power of 108 W with Q-switched pulses of 47 ns duration. The laser beam is characterized by an M2 factor of 2.5×2.7. A model of amplification, which takes into account the temporal overlap between the beams that propagate forwards and backwards in the amplifier stage, was developed to explain the experimental results. 相似文献
173.
174.
Andrea Stith T. Kevin Hitchens Denise P. Hinton Stuart S. Berr Bastiaan Driehuys James R. Brookeman Robert G. Bryant 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,139(2):225
We have investigated the transfer of polarization from 129Xe to solute protons in aqueous solutions to determine the feasibility of using hyperpolarized xenon to enhance 1H sensitivity in aqueous systems at or near room temperatures. Several solutes, each of different molecular weight, were dissolved in deuterium oxide and although large xenon polarizations were created, no significant proton signal enhancement was detected in
-tyrosine, α-cyclodextrin, β-cyclodextrin, apomyoglobin, or myoglobin. Solute-induced enhancement of the 129Xe spin–lattice relaxation rate was observed and depended on the size and structure of the solute molecule. The significant increase of the apparent spin–lattice relaxation rate of the solution phase 129Xe by α-cyclodextrin and apomyoglobin indicates efficient cross relaxation. The slow relaxation of xenon in β-cyclodextrin and
-tyrosine indicates weak coupling and inefficient cross relaxation. Despite the apparent cross-relaxation effects, all attempts to detect the proton enhancement directly were unsuccessful. Spin–lattice relaxation rates were also measured for Boltzmann 129Xe in myoglobin. The cross-relaxation rates were determined from changes in 129Xe relaxation rates in the α-cyclodextrin and myoglobin solutions. These cross-relaxation rates were then used to model 1H signal gains for a range of 129Xe to 1H spin population ratios. These models suggest that in spite of very large 129Xe polarizations, the 1H gains will be less than 10% and often substantially smaller. In particular, dramatic 1H signal enhancements in lung tissue signals are unlikely. 相似文献
175.
176.
对重复脉冲泵浦的管状YAG激光器的3维温度分布进行了深入研究,计算模拟了管状介质在不同时刻的3维动态温升分布。计算结果表明,泵浦初始阶段,介质中各点的瞬态温升均随泵浦脉冲个数呈锯齿形增长,最大温升点的位置由介质内壁随时间逐渐向介质内部移动;经过大约490个脉冲泵浦后,介质内的瞬态温升最终随时间呈重复周期性变化,最大温升点将不再移动。当温升分布呈重复周期性变化后,激光管中心部分的温升较大,内外壁的温升较小,且外壁温升低于内壁温升。 相似文献
177.
C2H2分子(X1∑g+,ν2”=1,J”)态mj定向布居及光学AC Stark效应 总被引:2,自引:1,他引:1
利用相干受激Raman抽运,选择性地激发C2H2分子单一振转态。在Raman泵浦与探测激光不同偏振条件下,获得紫外探测激光诱导的A^ ̄^1J(V′3=1)←-^ ̄Z^2Σ^+g,v′2=1,j″)荧光增益光谱,从而研究了C2H2分子单一振转态的光学AC Stark效应和mj的定向分布A0^(1),利用Stark线型加宽数值模型,从理论上计算得到的Raman线型与实验结果进行比较。 相似文献
178.
由弱磁场下光泵自旋交换、强磁场中核磁共振测量方法,获得激光极化低压同位素129Xe气体的核自旋弛豫率1/T1及其与N2气压力、环境温度的关系.结果表明:在291K的室温下,对于0~11 333.05Pa的N2气压力范围,1/T1随着N2气压力的增加而增大;N2气压力为1 466.63Pa时,1/T1随着样品温度从234K到292K增高而减小 相似文献
179.
高文斌 《化学物理学报(中文版)》2000,13(4)
利用受激Raman泵浦,使线性分子C2H2选择性地制备振动态角动量定向布居参数A0(1)达到0.7~0.8。并测定了角动量定向布居碰撞诱导的弛豫速率常数。采用园偏振的紫外激光诱导荧光方法,可表征分子角动量定向布居的制备和它的碰撞弛豫过程。 相似文献
180.
P.L. Chapovsky J. Cosléou F. Herlemont M. Khelkhal J. Legrand 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):297-301
A new method is proposed for the experimental determination of the hyperfine coupling in molecules. The method is based on
the level-crossing effect in the spin isomer conversion in alternating electric fields. An experiment performed with the 13CH3F molecules has revealed the strength of the off-diagonal in K () nuclear spin-spin coupling kHz, which is only by kHz larger than the theoretical value calculated on the basis of the molecular structure.
Received 25 January 2000 and Received in final form 11 May 2000 相似文献