Various damage mechanisms in carbon and silicon materials under femtosecond x-ray irradiation

TL;DR

This paper reviews damage mechanisms in carbon and silicon materials caused by femtosecond x-ray laser pulses, using a hybrid modeling approach to analyze various physical phenomena and compare with experimental data.

Contribution

It introduces the XTANT hybrid approach to model diverse damage mechanisms in materials under femtosecond x-ray irradiation, providing insights into thermal, nonthermal, Coulomb explosion, and ablation processes.

Findings

Identification of conditions for thermal melting and phase transitions.

Validation of the model through comparison with experimental optical data.

Predictions of diffraction patterns for future FEL experiments.

Abstract

We review the results of our research on damage mechanisms in materials irradiated with femtosecond free-electron-laser (FEL) pulses. They were obtained using our hybrid approach, XTANT (X-ray-induced Thermal And Nonthermal Transitions). Various damage mechanisms are discussed with respect to the pulse fluence and material properties on examples of diamond, amorphous carbon, C60 crystal, and silicon. We indicate conditions: producing thermal melting of targets as a result of electron-ion energy exchange; nonthermal phase transitions due to modification of the interatomic potential; Coulomb explosion due to accumulated net charge in finite-size systems; spallation or ablation at higher fluences due to detachment of sample fragments; and warm dense matter formation. Transient optical coefficients are compared with experimental data whenever available, proving the validity of our modeling approach. Predicted diffraction patterns can be compared with the results of ongoing or future FEL experiments. Limitations of our model and possible future directions of development are outlined.