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在采用7fs、770nm的激光脉冲进行的高次谐波实验中产生了光子能量约为90eV的单个软x光脉冲,并通过激光场中氪气的光电离过程对其进行了研究。在探测垂直于激光偏振方向的光电子能谱中,由于此方向上激光场引起的电子能谱展宽受到抑制,从而使研究人员能够观测到激光场引起的能谱移动,获得亚激光周期的时间分辨率。测量了脉宽为1.8fs(+0.7/-1.2fs)的单个X光脉冲,它比激光的振荡周期(2.6fs)还要短。本文采用的亚飞秒激光脉冲的产生和测量方法,对于很宽波长范围的X射线都是适用的,这为阿秒实验科学铺平了道路。探索比激发光场还要快的原子过程将不再是遥不可及的事。
A single soft X-ray pulse with a photon energy of about 90 eV was generated in a high-order harmonic experiment with a 7 fs laser pulse and a 770 nm laser pulse. The photonic ionization of krypton in the laser field was also studied. In detecting the photoelectron spectrum perpendicular to the laser polarization direction, the broadening of the electron spectrum due to the laser field in this direction is suppressed, so that the researchers can observe the spectral shift caused by the laser field and obtain the time-resolved sub-laser cycle rate. A single X-ray pulse with a pulse width of 1.8 fs (+0.7 / -1.2 fs) was measured, which is shorter than the laser oscillation period (2.6 fs). The method of generating and measuring sub-femtosecond laser pulses used in this paper is suitable for X-ray in a wide range of wavelengths, which paves the way for the experimental science of achenes. It will no longer be out of reach to explore an atomic process that is faster than the excitation field.