Among the strongly non-linear phenomena occurring in the interaction of intense laser fields with atoms and molecules High-order Harmonic Generation (HHG) is considered particularly important because of its possible application as a table top soft X-ray source. Within the strong field approximation (SFA) and single active electron model, which has been highly successful in explaining HHG in atoms, the emission from a single atom or molecule is found to be determined by the dipole formed between the bound state (essentially the field-free ground state) and the laser excited continuum state from which the recombination occurs. In this respect the nature of the ground state wavefunction is crucial [1]. The role of the ground state of the emitting species can be investigated by comparing harmonic spectra produced by molecules and by atoms with similar ionization potential (I p) [2]. In this work, XUV spectra from some alkanes (methane, I p = 12.97 eV; propane, I p = 11.07 eV; butane, I p = 10.63 eV) were measured and compared with those acquired from xenon (I p = 12.13 eV). The harmonic emission was obtained focusing femtosecond light pulses on a pulsed gas jet. Two different pulse duration were considered, namely 20 fs and 6 fs; in both the two cases the pulse energy could be continuously tuned without modification in temporal and spatial structure of the driving pulses.
High-order harmonic generation in alkanes: Signature of the ground state wavefunction
Vozzi C;Poletto L;
2005
Abstract
Among the strongly non-linear phenomena occurring in the interaction of intense laser fields with atoms and molecules High-order Harmonic Generation (HHG) is considered particularly important because of its possible application as a table top soft X-ray source. Within the strong field approximation (SFA) and single active electron model, which has been highly successful in explaining HHG in atoms, the emission from a single atom or molecule is found to be determined by the dipole formed between the bound state (essentially the field-free ground state) and the laser excited continuum state from which the recombination occurs. In this respect the nature of the ground state wavefunction is crucial [1]. The role of the ground state of the emitting species can be investigated by comparing harmonic spectra produced by molecules and by atoms with similar ionization potential (I p) [2]. In this work, XUV spectra from some alkanes (methane, I p = 12.97 eV; propane, I p = 11.07 eV; butane, I p = 10.63 eV) were measured and compared with those acquired from xenon (I p = 12.13 eV). The harmonic emission was obtained focusing femtosecond light pulses on a pulsed gas jet. Two different pulse duration were considered, namely 20 fs and 6 fs; in both the two cases the pulse energy could be continuously tuned without modification in temporal and spatial structure of the driving pulses.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
