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Title: Time of flight spectrometry studies of graphite surface : ultrafast laser ablation and photoelectron spectroscopy
Author: Huchon, Christophe Xavier
ISNI:       0000 0004 2685 3490
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2008
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This work reports an investigation of the interaction of ultrashort laser pulses with a graphite surface. Time-of-flight experiments were conducted with a 100 fs laser system, then 13 fs laser pulses at 800 nm wavelength were used for photoelectron spectroscopy studies. Multi-shots and single-shot laser pulse regimes have shown the existence of two mechanisms involved in the ablation of graphite: at low laser fluence, a non-thermal physical process known as Coulomb explosion (CE) is responsible for the ultrafast removal of particles. At high laser fluence, a thermal process, called plasma generation and characterized by a liquid-carbon phase initiated by the laser pulse, takes place and is believed to be at the origin of the ejection of particles. On the other hand, results from 13 fs laser pulses give rise to unusual high kinetic energy photoelectron around 20 eV that cannot be explained by the multiphoton ionization process but by tunnel and/or above barrier ionization (ABI). This unexpected result at such low intensities (10¹⁰ < I(W/cm²) <10¹²) is interpreted as a roughening of the surface by the laser pulse that leads to photon-plasmon coupling, then an enhancement of the local electric surface field enough to make possible electrons tunneling through the potential barrier or even to escape directly (ABI) into the vacuum.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics