Sampling measurement of soft-x-ray-pulse shapes by femtosecond sequential ionization of Kr+ in an intense laser field.
We propose a sampling technique for measuring the shape of ultrashort soft-x-ray pulses. The technique uses the transient state of Kr+ ions that is produced by the femtosecond sequential evolution of Kr ions during optical-field-induced ionization as an ultrafast x-ray-absorption sampling gate. We demonstrate the technique by measuring the pulse shape of the 51st harmonic (15.6 nm) generated by a 100-fs titanium:sapphire laser pulse. The measured pulse duration is 220 fs. Our experimental result confirms that the sequential evolution of Kr+ ions from neutral Kr to Kr2+ is the dominant contribution to the ionization process from the aspect of time-domain measurement.
Oguri
Katsuya
K
NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosoto Wakamiya, Atsugi, Kanagawa 243-0198, Japan. oguri@nttbrl.jp
Nishikawa
Tadashi
T
Ozaki
Tsuneyuki
T
Nakano
Hidetoshi
H