共查询到20条相似文献,搜索用时 218 毫秒
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利用YAG激光抽运的染料激光器将钾原子由基态 4S双光子共振激发到 6S态 ,研究了钾原子 4S 6S双光子共振三光子电离的电离谱与温度、激光强度的关系 ,发现电离流的强度随着温度的升高而增强 ,当温度在 370℃附近时达到最大值 ,此时温度继续升高电离流强度减弱。在温度不变的情况下 ,电离流强度随着激光能量的增强而增强 ,当激光强度为 4 5× 10 5W /mm2 时到达最大值 ,继续增加激光强度 ,电离流强度趋于饱和。实验中观测到对应于 6S 4P的自发辐射 相似文献
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230—245nm范围内Cl原子共振增强多光子电离光谱 总被引:1,自引:0,他引:1
利用共振增强多光子电离--时间飞行质谱技术获得了Cl原子在230-245nm范围内的代振增强多光子电离光谱,共观察到26条谱线,其中5条是作者新观察到的,这些谱线对应从Cl原子基态到激发态的双光子跃迁。从中还观察到Cl原子在强电场中的Stark效应,发现在强场条件下,Cld原子绵基太^2P1/2^0和^2P3/2^0两能级之间的能工位移1.35cm^=1。而各电子激发态的Stark位移则大致相等, 相似文献
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利用单电子近似下锂原子精确的模型势,通过数值求解三维含时薛定谔方程的方法,研究了锂原子在激光场中发射低阶谐波的性质,研究结果表明,对于锂原子电离阈值以下的低阶谐波,除了通常的奇次谐波外,还有侧峰结构出现,运用同步压缩变换技术(SST)分析这些低阶谐波的辐射特性,我们发现这些侧峰是由原子在激光场中的缀饰态之间的跃迁和无场下激发态到基态的跃迁组成的,如果当激光脉冲结束后,仍有发射的侧峰,其位置与主峰之间的能量差可以用来估算原子激发态在激光场中的最大Stark移动. 相似文献
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根据量子力学微扰理论给出了相干扰激发电离情形下双光子共振三光子近共振和双光子近共振三光子共振这两种两光子电离过程的电离截面表达式,表明这两种过程的离子强度与它们的起始能级有关,根据这一结论分析了实验测得的对氟甲苯分子的多光子电离谱,结果表明获得该电离谱的过程为三光子共振四光子电离过程。 相似文献
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钠蒸气中的双光子共振三光子电离和双光子混合并振三光子电离 总被引:2,自引:2,他引:0
在钠原子-分子混合样品中,分别运用双光子共振三光子电离以及双光子混合共振三光子电离,测得了钠原子4D态的电离流时间衰减曲线。由电离流与多光子动力学参数的关系,得到了4D态的光电离截面。 相似文献
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用单色双光子共振电离方法研究了乙基苯的第一激发态的振动光谱. 从基态跃迁到第一激发态的带源位置出现在37586 cm-1处.获得的第一激发态振动光谱超过了2000 cm-1,并观察到了几个乙基取代基的扭转振动和与苯相似的正则振动. 同时,用含时密度泛函理论和单组态相互作用(CIS)方法计算了第一激发态的跃迁能量,用Hartree-Fock和CIS方法优化了基态和第一激发态分子结构,预测了振动频率. 基态和激发态结构的优化结果均显示为顺式结构,即乙基取代基的对称面垂直了苯基平面. 相似文献
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测定硅原子共振谱线精细结构相对强度 总被引:1,自引:1,他引:0
原子光谱实验应主要了解谱线波长和谱线强度两个问题。前者涉及原子能级结构,后者涉及原子能级之间跃迁概率;二者紧密联系,是了解原子结构的二个方面。原理共振谱线是指从最低激发态直接跃迁到基态的谱线。硅原子基态是[Ne]3s~23p~2[~3P],三重态的最低激发态是[Ne]3s~23p4s[~3P],共振跃迁如右图所示。当精细分裂不大时,温度对ν~4影响很小,则A可视为常数。对于L→L跃迁,精细结构强度的理论计算为经计算,获得的硅原子共振线精细结构强度列表如下。 相似文献
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本文首次报道了用共振多光子电离(RMPI)技术探测到四条在可见光范围内的Gd原子强双光子跃迁线.观察到双色三光子Gd原子激光同位素分离.研究了高分辨率Gd原子电离谱,并解释了电离谱的线型. 相似文献
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在He~+离子1s态和2s态的叠加态作为初始态时,提出一种优化3束激光场来增大谐波截止能量和强度的方法.结果表明:在叠加初始态下,谐波强度要比基态初始态下增强3个数量级以上.随后,在3色场波形优化下,谐波截止能量又得到增大,进而获得一个高强度、高光子能量的谐波光谱连续区.通过叠加光谱连续区上最后100次的谐波可以获得一个27 as的孤立阿秒脉冲. 相似文献
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We theoretically study the generation of high-order harmonics and attosecond pulses from the superposition of an initial state in helium atom driven by a three-color laser field. It is shown that when the initial state is chosen to be a single electronic state, due to the rapid depletion of the ground state, the efficiency of the spectral continuum will be decreased as the initial state increases. When the initial state is chosen to be the coherent superposition of the ground state and an arbitrary excited state, the efficiency of the spectral continuum can be enhanced compared to that from the single initial state. Further, with the optimization of the three-color laser beam, not only can the harmonic cutoff be extended to the water window X-ray region but also the spectral continuum is contributed by the single harmonic emission peak with the dominant short quantum path. Consequently, two combinations of the laser parameters can be found to generate the water window spectral continuum. By properly superposing some harmonics on the spectral continuum, a number of intense water window pulses with the duration of sub-35 as can be produced. 相似文献
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In this paper, we theoretically investigate high-order harmonic generation (HHG) from a helium atom prepared in a coherent superposition state in a two-color laser field. Numerical results show that the emission efficiency of the harmonic spectrum in a coherent superposition state is enhanced by approximately eight orders of magnitude compared with the case of the ground state. In addition, the effect of the initial population of the excited state on the HHG is presented to reveal the physical origin of the enhancement of HHG. By adjusting the laser parameters of the driving pulse, such as the chirping parameter, the relative phase, and the intensity of the driving pulse, an ultrabroad continuum with a width of 275 eV can be observed. Finally, an isolated 12-as pulse is generated after phase compensation. 相似文献
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Quantum path control using attosecond pulse trains via UV-assisted resonance enhance ionization 下载免费PDF全文
We theoretically investigate the quantum path selection in an ultraviolet(UV)-assisted near-infrared field with an UV energy below the ionization threshold. By calculating the ionization probability with different assistant UV frequencies, we find that a resonance-enhanced ionization peak emerges in the region Euv < Ip, where Euv is the photon energy and Ip is the ionization energy. With an attosecond pulse train(APT) centered in the resonance region, we show that the short quantum path can be well selected in the continuum case. By performing the electron trajectory analysis, we have further explained the physical mechanism of the quantum path selection. Moreover, we also demonstrate that in the resonance region, the harmonic emission from the selected paths is more efficient than that with the APT energy above the ionization threshold. 相似文献
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Harmonic Enhancement Mechanism of a Superposition State Atom Irradiated by Short Pulses 总被引:1,自引:0,他引:1 下载免费PDF全文
We investigate the high-order harmonic generation (HHG) of a model atom whose initial state is prepared in a superposition of its ground state and an excited state irradiated by different duration laser pulses. Compared to the HHG generated from an atom whose initial state is in its ground state, its conversion efficiency obtains some enhancement. The enhancement originates from the higher ionization rate (rather than the ionization yield) of the atom with superposition initial state. 相似文献
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本文研究了由体系的基态和较高激发态迭加形成的原子在强激光场作用下的高次谐波发射.观察电离波包的演化过程,阐明了谐波发射效率提高的原因.在给定入射激光条件下,通过选择不同的激发态,可以实现对谐波发射的控制. 相似文献
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Decoding the electron dynamics in high-order harmonic generation from asymmetric molecular ions in elliptically polarized laser fields 下载免费PDF全文
Cai-Ping Zhang 《中国物理 B》2022,31(4):43301-043301
The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born-Oppenheimer model with two-dimensional electron dynamics. It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields. The periodical character is ellipticity-dependent. By establishing the physical image, the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state. Furthermore, the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field. The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field. 相似文献