1. 1D-H2 e 3D-H2+ Molecola d'idrogeno sottoposta a campo di radiazione laser
G. Castiglia1, P.P. Corso1, R. Daniele1, E. Fiordilino1, F. Morales2, F. Persico1
1 DSFA – Università degli Studi di Palermo
2 DIFTER – Università degli Studi di Palermo
Incontro finale con referee del progetto PI2S2
Palermo

2. Research area Atoms and molecules in strong laser fields
The physics of laser-matter interaction in the presence of strong laser pulses has recently undergone considerable advances particularly in the study of nonlinear phenomena. Among these:
high-order harmonic generation (HHG);
molecular ionization, molecular dissociation, Coulomb explosion;
charge resonance enhanced ionization (CREI);
HHG applications
source of XUV ligth
spectroscopic tools
attosecond pulse generation
The laser-matter interaction is not easy to investigate using a purely theoretical and analytical approach.
In the last two decades, the numerical approach has made great improvements in providing a solution to the Time-Dependent Schroedinger Equation (TDSE) of relatively complex systems such as small molecules.
Palermo, Incontro finale con referee del progetto PI2S2 ,

3. Research area Atoms and molecules in strong laser fields
Our interest has been focused on the study of the dynamics and the radiation emitted by H2+ molecular ion, H2 molecule and their isotopes subjected to strong laser fields.
Objectives:
Study of HHG
Monitoring molecular dynamic
Molecular imaging
Investigation of molecular dissociation
Practical techniques for attosecond pulse generation
Isotopic effects
The TDSE
has been numerically solved by using the Split-Operator Method (SOM).
The SOM consists on the approximation of the time evolution of the wave equation by means of the following scheme:
Palermo, Incontro finale con referee del progetto PI2S2 ,

4. Grid integration Numerical code: Split-Operator method
2D and 3D Split-Operator Parallel Code (MPI) for the numerical solution of the TDSE.
1D_H2 - MPI code for a 1D H2 molecole (2 degrees of freedom)
3D_H2+ - MPI code for a 3D H2+ molecolar ion (3 degrees of freedom)
Split-Operator method
massive use of FFT
Performance improvement by using the FFTW libraries
Execution:
2D and 3D parallel simulations on 16/512 processors on the Gigabit and Infiniband networks
elapsed time for a 3D MPI code on 256 processors: 6 h
CPU time 1536 h = 64 days
memory used 5 GByte
elapsed time for a 2D MPI code on 64 processors: 18 h
CPU time 1152 h = 48 days
memory used 2 GByte
Palermo, Incontro finale con referee del progetto PI2S2 ,

5. Results
Different molecular isotopes are characterized by different satellite peak spacing. Each satellite peak spacing is directly related to the corresponding nuclear vibration frequency
In addition to the satellite peaks the molecular isotopes are characterized by different heights of the emitted spectrum in the plateau region.
Palermo, Incontro finale con referee del progetto PI2S2 ,

6. Results
Probability density of the ground state of a 1-D H2 Molecule.
Single and double ionization signals for both fixed and moveable nuclei of a 1-D H2 Molecule.
The profile of the ionization signals drastically changes going from fixed to moving nuclei. In particular double ionization signal is strongly increased in the case of moving nuclei, probably because the dynamics of the nuclei reaches a region of enhanced ionization.
Palermo, Incontro finale con referee del progetto PI2S2 ,

7. Publications
Castiglia G., Corso P. P., Daniele R., Fiordilino E., Morales F., Orlando G., Control of Electron Motion in a Molecular Ion: Dynamical Creation of a Per-manent Electric Dipole. Laser Phys., 17, (2007)
Orlando G, Castiglia G., Corso P.P., Fiordilino E., Bremsstrahlung from a repulsive potential: attosecond pulse generation. J. Phys. B: At. Mol. Opt. Phys, 41, (2008)
Morales F., Castiglia G., Corso P.P., Daniele R., Fiordilino E., Orlando G., Persico F., Evidence of Nuclear Motion in H2-like Molecules by Means of High Harmonic Generation. Laser Phys., 18, (2008)
Castiglia G., Corso P.P., Fiordilino E., Persico F., Rescattering and vibrations in homonuclear diatomic molecules in a strong electromagnetic field. Phys. Lett. A, 373, (2009)
Daniele R., Castiglia G., Corso P.P., Fiordilino E., Morales F., Orlando G., Nuclear molecular dynamics investigated by using high-order harmonic generation spectra. J. Mod. Optic, 56, (2009)
Camiolo G., Castiglia G., Corso P.P., Fiordilino E., Marangos J. P., Two-electron systems in strong laser fields. Phys. Rev. A, 79, (2009)
Daniele R., Morales F., Castiglia G., Corso P.P., Fiordilino E., Orlando G. On the control of the HHG spectrum emitted by a homonuclear diatomic molecule via the laser polarization. (Accepted for the publication on J. Opt. Soc. Am. B)
Palermo, Incontro finale con referee del progetto PI2S2 ,