Accessibility Tools

X-ray seminar

Seminarium Rentgenowskie Stacjonarnie

Observation of picosecond melting of Pd films using X-ray free electron laser pulses

31-10-2023 10:30 - 12:00
Venue
Instytut Fizyki PAN, Sala D, Budynek I
Speaker
dr hab. inż. prof. ucz. Jerzy Antonowicz
Affiliation
Wydział Fizyki, Politechnika Warszawska
Sala
Sala D

Due to its extremely short timescale, the non-equilibrium melting of metals is exceptionally difficult to probe experimentally. The knowledge of melting mechanisms is thus, to a large extent, based on the results of theoretical predictions and computer modeling. This talk reports on the ultrafast melting of thin polycrystalline Pd films studied by an optical laser pump – X-ray free-electron laser probe technique and two-temperature model molecular dynamics simulations. By acquiring the X-ray diffraction snapshots with sub-picosecond resolution, we capture the sample’s atomic structure during its transition from the crystalline to the liquid state. Bridging the timescales of the experiment and the simulation allows us to formulate a realistic microscopic picture of the melting transition. We demonstrate that the melting process gradually accelerates with the increasing density of deposited energy. The molecular dynamics simulations reveal that the transition mechanism progressively varies from heterogeneous, initiated inside the material at structurally disordered grain boundaries, to homogenous, proceeding catastrophically in the crystal volume on a picosecond timescale comparable to that of electron-phonon coupling. Even though the shortest observed melting time in Pd is an order of magnitude smaller than in gold, the melting mechanism of both metals remains similar. We conclude that the rate of laser-induced melting of thin polycrystalline Pd film is, as in gold, limited by the timescale of lattice heating. Our work highlights the role of crystal defects, either pre-existing as grain boundaries or generated on heating, in the melting transition.

 
 

List of Dates (Page event details)

  • 31-10-2023 10:30 - 12:00
Save
Cookies user preferences
We use cookies to ensure you to get the best experience on our website. If you decline the use of cookies, this website may not function as expected.
Accept all
Decline all
Read more
Essential
Essential cookies
These cookies are necessary for the correct operation of the website and therefore cannot be disabled on this level; the use of these cookies does not involve the processing of personal data. While you can disable them via your browser settings, doing so may prevent the website from working normally.
Accept
Analytical cookies
These cookies are particularly intended to enable the website administrator to monitor the website traffic statistics, as well as the sources of traffic. Such data is typically collected anonymously.
Google Analytics
Accept
Decline