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Molecules in a laser field:semiclassical & quantal treatmentE. Fiordilino*§,G. Castiglia*§, P. P. Corso*§, R. Daniele, F. Morales, G. Orlando* and F. Persico*§* CNISM and Dipartimento di Scienze Fisiche ed Astronomiche, Via Archirafi 36, 90123 Palermo, Italy.§ Consorzio COMETA - Research Line: Atoms in Strong Fields, Dipartimento di Scienze Fisiche ed Astronomiche, Via Archirafi 36, 90123 Palermo, Italy. C N I S M ISCHIA 2009
High Harmonic Generation ISCHIA 2009
Diffused radiation Molecule Laser Artistic spectrum ISCHIA 2009
Fullerene ISCHIA 2009
Pulse duration 64 oc ISCHIA 2009
Cutoff law at low field ISCHIA 2009
Diatomic molecules in a laser field ISCHIA 2009
Full hamiltonian ISCHIA 2009
H2+Classical nuclei ISCHIA 2009
Schroedinger equation for the electron Newton equation for the nuclei Hamiltonian electron nuclei interaction nucleus-nucleus interaction ISCHIA 2009
It is evident the presence of regularly spaced sidebands around the odd harmonic peaks The satellite peak spacing is exactly given by the nuclei vibration frequency ISCHIA 2009
1D model for various molecular isotopes Different molecular isotopes are characterized by different satellite peak spacing Each satellite peak spacing is directly related to the corresponding nuclear vibration frequency ISCHIA 2009
Fixed nuclei: spectrum for M=M0 No side-bands around the odd harmonic lines of HHG are present ISCHIA 2009
Schroedinger equation in 3D The presence of the satellite peaks in the harmonic spectrum does not depend upon the dimensionality of the model. The harmonic lines present side peaks whose separation scales as ISCHIA 2009
H2 ISCHIA 2009
1D semiclassical model for various H2 molecular isotopes ISCHIA 2009
1D full quantum calculations for H2+ ISCHIA 2009
Conceptual considerations suggest the use of a full quantal calculation for the molecule. ISCHIA 2009
ΔωN ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 ISCHIA 2009
1D full-quantum model for various H2+ isotopes T = 4 o.c. ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 For short pulses heavy nuclei win ISCHIA 2009
1D full-quantum model for various H2+ molecular isotopes T = 8 o.c. ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 ISCHIA 2009
1D full-quantum model for various H2+ molecular isotopes T = 16 o.c. ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 For long pulse light nuclei win ISCHIA 2009
1D full-quantum model for various H2+ molecular isotopes T = 32 o.c. ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 ISCHIA 2009
1D full-quantum model for various H2+ isotopes T = 64 o.c. ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 ISCHIA 2009
1D full quantum calculations for molecular ions oscillations of the nuclei spread of the nuclear wavefunction ____ M = M0 ____ M = 4 M0 ____ M = 16 M0 ISCHIA 2009
Ionization Signal Nuclear wavefunction spread Isotopiceffect: the intensity of the harmonics decreases by increasing the mass of the nuclei Possible explanation: Nuclear wavefunction for lighter nuclei easily spreads and crosses a region of R with enhanced ionization ISCHIA 2009
ISOTOPIC EFFECT SHORT LASER PULSE: The intensity of harmonics increases by decreasing nuclear mass LONG LASER PULSE: The intensity of harmonics decreases by decreasing nuclear mass The nuclear wavefunction does not reach the critical ionization region The nuclear wavefunction approaches the critical ionization region ISCHIA 2009
CONCLUSIONS • Fullerene should emit harmonics: I hope experiments will • come soon. • The motion of the nuclei introduces in the HHG spectrum • satellite peaks of the odd-harmonics. The presence of the • side-peaks is a direct evidence of the nuclear vibration • motion. • A full quantum model shows an isotopic effect in the • HHG spectra. References: N. L. Wagner, A. Wüest, I. P. Christov, T. Popmintchev, X. Zhou, M. M. Murnane, H. C. Kapteyn, PNAS 103, 13279 (2006). P. P. Corso, E. Fiordilino, F. Persico, JPB 40, 1383 (2007). S. De Luca and E. Fiordilino, J. Phys. B: At. Mol. Opt. Phys. 29, 3277 (1996). ISCHIA 2009