Production of doubly charged helium ions by two-photon absorption of an intense sub-10-fs soft x-ray pulse at 42 eV photon energy.
Production of doubly charged helium ions by two-photon absorption of an intense sub-10-fs soft x-ray pulse at 42 eV photon energy.
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DOI：
10.1103/physrevlett.94.043001
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发表时间：
2005-01
影响因子：
8.6
通讯作者：
Y. Nabekawa;H. Hasegawa;E. Takahashi;K. Midorikawa
中科院分区：
文献类型：
--
作者：
Y. Nabekawa;H. Hasegawa;E. Takahashi;K. Midorikawa
报道了利用钛宝石激光器飞秒脉冲的27次谐波产生的光子能量为42 eV的氦原子与光子之间的非线性相互作用产生的双电荷氦离子的观测结果。离子的数目与第27次谐波脉冲的强度的平方成正比，因此与通过单电荷离子伴随的顺序电离的其他非线性过程相比，双光子双电离应占主导地位。利用这种现象，通过使用自相关技术来测量第27次谐波脉冲的脉冲持续时间，据我们所知，这是第一次，结果发现持续时间为8 fs。
We report on the observation of doubly charged helium ions produced by a nonlinear interaction between a helium atom and photons with a photon energy of 42 eV which are generated with the 27th harmonic of a femtosecond pulse from a Ti:sapphire laser. The number of ions is proportional to the square of the intensity of the 27th harmonic pulse, and thus two-photon double ionization should be dominantly induced as compared with other nonlinear processes accompanying sequential ionization via a singly charged ion. This phenomenon is utilized to measure the pulse duration of the 27th harmonic pulse by using an autocorrelation technique, for the first time to our knowledge, and as a result a duration of 8 fs is found.