Time of flight measurement of femtosecond ablation of graphite Christophe Huchon Nanoscale Physics Research Laboratory School of Physics and Astronomy The University of Birmingham United Kingdom Attosecond meeting, 7 december 2005, Rutherford Appleton Laboratory

Motivation: mechanism(s) in femtosecond laser ablation ? TOF Products ONLY from surface ? TOF Products from surface + fragmentation ? Thermal (equilibrium) or/and coulomb explosion (non equilibrium)?

LAYOUT PUMP-PROBE Nd:YLF 1 kHz l = 527 nm Up to 25 mJ Ti:Sapphire, Regenerative Amplifier 1 kHz 100 fs Up to 2 mJ Ti:Sapphire, 82 MHz, 800 nm, 100 fs, 600 mW Ar+ laser All lines 6 W Argon gas flow Transfer arm PMT Differential pumping chamber STM Ablation Time-of-flight spectrometer HHG LAYOUT PUMP-PROBE

Principle of TOF spectrometer D Source/extraction Drift region Detector E2 = 0 E1 = V/s V  Ions desorbed from surface: if D >> s

Model used for ablation process

pulse= 100 fs Epulse= 200 J Usample= 500 V Ratio ≈ 11

pulse= 100 fs Epulse= 10.5 J Usample= 405 V

KE distribution spread as a function of the voltage pulse= 100 fs Epulse= 10.5 J

Summary fragmentation process involved in the ablation of the graphite with femtosecond laser pulse. need to find what is the rate thermal vaporization / Coulomb explosion  VUV probe VUV, XUV will allow time-resolved photoelectron emission

Acknowlegdement Andrey Kaplan Miklos Lenner Quanmin Guo Richard Palmer