Subnanosecond phase transition dynamics in laser-shocked iron
Huijeong Hwang, Eric Galtier, Hyunchae Cynn, Intae Eom, Sae Hwan Chun, Yoonah Bang, Gil Chan Hwang, Jinhyuk Choi, Taehyun Kim, Mihye Kong, Soyeon Kwon, Kyung Shin Kang, Hae Ja Lee, Changkun Park, Jae Il Lee, Yongmoon Lee, Yongmoon Lee, Wenge Yang, Sang‐Heon Shim, Thomas Vogt, Sangsoo Kim, Jaeku Park, Sunam Kim, Daewoong Nam, Jeongki Lee, H.J. Hyun, Minseok Kim, T. Y. Koo, C.-C. Kao, Toshimori Sekine, Yongjae Lee, Yongjae Lee
Abstract
Iron is one of the most studied chemical elements due to its sociotechnological and planetary importance; hence, understanding its structural transition dynamics is of vital interest. By combining a short pulse optical laser and an ultrashort free electron laser pulse, we have observed the subnanosecond structural dynamics of iron from high-quality x-ray diffraction data measured at 50-ps intervals up to 2500 ps. We unequivocally identify a three-wave structure during the initial compression and a two-wave structure during the decaying shock, involving all of the known structural types of iron (α-, γ-, and ε-phase). In the final stage, negative lattice pressures are generated by the propagation of rarefaction waves, leading to the formation of expanded phases and the recovery of γ-phase. Our observations demonstrate the unique capability of measuring the atomistic evolution during the entire lattice compression and release processes at unprecedented time and strain rate.