Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses

J. Chalupsky (1, 2) , L. Juha (1) , V. Hájková (1) , J. Cihelka (1) , L. Vyšín (1, 2) , J. Gautier (3) , J. Hajdu (4) , S. P. Hau-Riege (5) , M. Jurek (6) , J. Krzywinski (6) , R. A. London (5) , E. Papalazarou (3) , J.B. Pelka (6) , G. Rey (3) , Stéphane Sebban (3) , R. Sobierajski (6) , N. Stojanovic (7) , K. Tiedtke (7) , S. Toleikis (7) , T. Tschentscher (7) , C. Valentin (3) , H. Wabnitz (7) , Philippe Zeitoun (3)

1 PALS - Institute of Physics
2 CTU - Czech Technical University in Prague
3 LOA - Laboratoire d'optique appliquée
4 Laboratory of Molecular Biophysics [Uppsala]
5 LLNL - Lawrence Livermore National Laboratory
6 Institute of Physics in Poland
7 DESY - Deutsches Elektronen-Synchrotron [Hamburg]

We report the first observation of single-shot soft x-ray laser induced desorption occurring below the ablation threshold in a thin layer of poly (methyl methacrylate) - PMMA. Irradiated by the focused beam from the Free-electron LASer in Hamburg (FLASH) at 21.7nm, the samples have been investigated by atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze single-shot imprints in PMMA. An intermediate regime of materials removal has been found, confirming model predictions. We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32nm. Short-time exposure imprints provide sufficient information about transverse beam profile in HOH's tight focus whereas long-time exposed PMMA exhibits radiation-initiated surface ardening making the beam profile measurement infeasible.

Domains: Physics [physics]; Physics [physics]; Optics [physics.optics]

J. Chalupsky, L. Juha, V. Hájková, J. Cihelka, L. Vyšín, et al.. Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses. Optics Express, 2008, 17 (1), pp.208-217. ⟨10.1364/OE.17.000208⟩. ⟨hal-00508903⟩