Nanoplasma Formation by High Intensity Hard X-rays

Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at ~5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo- and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays.

[1]  E. Cohen.  Statistics and dynamics , 2002 .

[2]  R. D. Levine,et al.  Delayed ionization and fragmentation en route to thermionic emission: statistics and dynamics. , 2000, Annual review of physical chemistry.

[3]  Rudd,et al.  Binary-encounter-dipole model for electron-impact ionization. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[4]  Georg Weidenspointner,et al.  Self-terminating diffraction gates femtosecond X-ray nanocrystallography measurements , 2011, Nature Photonics.

[5]  E. Weckert,et al.  Energetics, ionization, and expansion dynamics of atomic clusters irradiated with short intense vacuum-ultraviolet pulses. , 2008, Physical review letters.

[6]  J. Tisch,et al.  High Energy Ion Explosion of Atomic Clusters: Transition from Molecular to Plasma Behavior , 1997 .

[7]  J. Hajdu,et al.  Explosions of xenon clusters in ultraintense femtosecond x-ray pulses from the LCLS free electron laser. , 2012, Physical review letters.

[8]  Gyula Faigel,et al.  Dynamics in a cluster under the influence of intense femtosecond hard X-ray pulses , 2004 .

[9]  G. Potdevin,et al.  Nanoplasma dynamics of single large xenon clusters irradiated with superintense x-ray pulses from the linac coherent light source free-electron laser. , 2012, Physical review letters.

[10]  W. H. Benner,et al.  Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight , 2012, Nature.

[11]  Chao Zhang,et al.  A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region , 2008 .

[12]  T. Fennel,et al.  Ionization heating in rare-gas clusters under intense XUV laser pulses , 2010, 1005.4004.

[13]  Charge recombination in soft x-ray laser produced nanoplasmas , 2008 .

[14]  M. Nagasono,et al.  Photoelectron angular distributions in infrared one-photon and two-photon ionization of FEL-pumped Rydberg states of helium , 2013 .

[15]  H. Wabnitz,et al.  Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser , 2002, Nature.

[16]  T. Möller,et al.  CLULU: An experimental setup for luminescence measurements on van der Waals clusters with synchrotron radiation , 1993 .

[17]  Tamar Schlick,et al.  Inherent speedup limitations in multiple time step/particle mesh Ewald algorithms , 2003, J. Comput. Chem..

[18]  B. Erk,et al.  Sequential multiphoton multiple ionization of atomic argon and xenon irradiated by x-ray free-electron laser pulses from SACLA , 2013 .

[19]  C. Bostedt,et al.  Femtosecond X-ray-induced explosion of C60 at extreme intensity , 2014, Nature Communications.

[20]  Takashi Kimura,et al.  Imaging live cell in micro-liquid enclosure by X-ray laser diffraction , 2014, Nature Communications.

[21]  R. Santra,et al.  Incoherent x-ray scattering in single molecule imaging , 2014, 1407.7670.

[22]  T. Ishikawa,et al.  A compact X-ray free-electron laser emitting in the sub-ångström region , 2012, Nature Photonics.

[23]  M. Yao,et al.  Deep inner-shell multiphoton ionization by intense x-ray free-electron laser pulses. , 2012, Physical review letters.

[24]  C. Bostedt,et al.  Shell explosion and core expansion of xenon clusters irradiated with intense femtosecond soft x-ray pulses , 2009 .

[25]  A. Rudenko,et al.  Frustration of direct photoionization of Ar clusters in intense extreme ultraviolet pulses from a free electron laser , 2009 .

[26]  Perry,et al.  Interaction of intense laser pulses with atomic clusters. , 1996, Physical review. A, Atomic, molecular, and optical physics.

[27]  R. Santra,et al.  Towards Realistic Simulations of Macromolecules Irradiated under the Conditions of Coherent Diffraction Imaging with an X-ray Free-Electron Laser , 2015 .

[28]  C. Bostedt,et al.  Emission of electrons from rare gas clusters after irradiation with intense VUV pulses of wavelength 100 nm and 32 nm , 2009 .

[29]  J. Rost,et al.  Mechanisms of cluster ionization in strong laser pulses , 2006 .

[30]  U. Buck,et al.  Cluster size determination from diffractive He atom scattering , 1996 .

[31]  C. Bostedt,et al.  Fast electrons from multi-electron dynamics in xenon clusters induced by inner-shell ionization , 2010 .

[32]  Ryszard S. Romaniuk,et al.  Operation of a free-electron laser from the extreme ultraviolet to the water window , 2007 .

[33]  David H. Parker,et al.  Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and photofragment ion imaging of molecular oxygen , 1997 .

[34]  F. Bijkerk,et al.  Angle-resolved photoelectron spectroscopy of sequential three-photon triple ionization of neon at 90.5 eV photon energy , 2011 .

[35]  T. Ishikawa,et al.  Crossover in the photoionization processes of neon clusters with increasing EUV free-electron-laser intensity , 2013 .

[36]  K. Gubbins,et al.  Adsorption and dynamics of argon in porous carbons , 2007 .

[37]  Hirotada Ohashi,et al.  Beamline, experimental stations and photon beam diagnostics for the hard x-ray free electron laser of SACLA , 2013 .

[38]  H. Chapman,et al.  Limitations of coherent diffractive imaging of single objects due to their damage by intense x-ray radiation , 2012 .

[39]  Garth J. Williams,et al.  Single mimivirus particles intercepted and imaged with an X-ray laser , 2011, Nature.

[40]  K. Meiwes-Broer,et al.  Laser-driven nonlinear cluster dynamics , 2009, 0904.2706.

[41]  C. Bostedt,et al.  Multistep ionization of argon clusters in intense femtosecond extreme ultraviolet pulses. , 2008, Physical review letters.

[42]  Garth J. Williams,et al.  Size-dependent ultrafast ionization dynamics of nanoscale samples in intense femtosecond x-ray free-electron-laser pulses. , 2012, Physical review letters.

[43]  R. Santra,et al.  Applicability of the classical molecular dynamics method to study x-ray irradiated molecular systems , 2014 .

[44]  W. Obert,et al.  Cluster Formation in Expanding Supersonic Jets: Effect of Pressure, Temperature, Nozzle Size, and Test Gas , 1972 .

[45]  T. Fennel,et al.  Rare-gas clusters in intense VUV, XUV and soft x-ray pulses: signatures of the transition from nanoplasma-driven cluster expansion to Coulomb explosion in ion and electron spectra , 2010, 1011.2069.

[46]  J. Rost,et al.  Slow and fast multi-photon ionization of clusters in strong XUV and X-ray pulses , 2013 .

[47]  Georg Weidenspointner,et al.  Femtosecond X-ray protein nanocrystallography , 2011, Nature.

[48]  H. Chapman,et al.  Heterogeneous clusters as a model system for the study of ionization dynamics within tampered samples , 2011 .

[49]  D. Ratner,et al.  First lasing and operation of an ångstrom-wavelength free-electron laser , 2010 .

[50]  T. Brabec,et al.  Fully microscopic analysis of laser-driven finite plasmas using the example of clusters , 2012 .