Laser Phase Control of HighOrder Harmonic Generation at Large Internuclear Distance: The H{sup +}H{sub 2}{sup +} System
Abstract
Exact (BornOppenheimer) 3D numerical solutions of the timedependent Schroedinger equation are obtained for the one electron linear H{sup +}H{sub 2}{sup +} atommolecule system at large internuclear distance R in interaction with twocycles intense (I>10{sup 14} W cm{sup 2}) 800 nm laser pulses. Highorder harmonic generation (HHG) spectra are obtained with an energy cutoff larger than the atomic maximum of I{sub p}+3U{sub p}, where I{sub p} is the ionization potential and U{sub p} is the ponderomotive energy. At large R, this extended cutoff is shown to be related to the nature of electron transfer, whose direction is shown to depend critically on the carrierenvelope phase (CEP) of the ultrashort pulse. Constructive and destructive interferences in the HHG spectrum resulting from coherent superpositions of electronic states in the H{sup +}H{sub 2}{sup +} system are interpreted in terms of multiple electron trajectories extracted from a time profile analysis.
 Authors:
 Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R2 (Canada)
 Publication Date:
 OSTI Identifier:
 20861578
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevLett.98.013001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BORNOPPENHEIMER APPROXIMATION; ELECTRON TRANSFER; ELECTRONS; HARMONIC GENERATION; HYDROGEN IONS 1 PLUS; HYDROGEN IONS 2 PLUS; INTERFERENCE; IONIZATION POTENTIAL; NUMERICAL SOLUTION; PONDEROMOTIVE FORCE; SCHROEDINGER EQUATION; THREEDIMENSIONAL CALCULATIONS; TIME DEPENDENCE; TRAJECTORIES
Citation Formats
Bandrauk, Andre D., Barmaki, Samira, and Kamta, Gerard Lagmago. Laser Phase Control of HighOrder Harmonic Generation at Large Internuclear Distance: The H{sup +}H{sub 2}{sup +} System. United States: N. p., 2007.
Web. doi:10.1103/PHYSREVLETT.98.013001.
Bandrauk, Andre D., Barmaki, Samira, & Kamta, Gerard Lagmago. Laser Phase Control of HighOrder Harmonic Generation at Large Internuclear Distance: The H{sup +}H{sub 2}{sup +} System. United States. doi:10.1103/PHYSREVLETT.98.013001.
Bandrauk, Andre D., Barmaki, Samira, and Kamta, Gerard Lagmago. Fri .
"Laser Phase Control of HighOrder Harmonic Generation at Large Internuclear Distance: The H{sup +}H{sub 2}{sup +} System". United States.
doi:10.1103/PHYSREVLETT.98.013001.
@article{osti_20861578,
title = {Laser Phase Control of HighOrder Harmonic Generation at Large Internuclear Distance: The H{sup +}H{sub 2}{sup +} System},
author = {Bandrauk, Andre D. and Barmaki, Samira and Kamta, Gerard Lagmago},
abstractNote = {Exact (BornOppenheimer) 3D numerical solutions of the timedependent Schroedinger equation are obtained for the one electron linear H{sup +}H{sub 2}{sup +} atommolecule system at large internuclear distance R in interaction with twocycles intense (I>10{sup 14} W cm{sup 2}) 800 nm laser pulses. Highorder harmonic generation (HHG) spectra are obtained with an energy cutoff larger than the atomic maximum of I{sub p}+3U{sub p}, where I{sub p} is the ionization potential and U{sub p} is the ponderomotive energy. At large R, this extended cutoff is shown to be related to the nature of electron transfer, whose direction is shown to depend critically on the carrierenvelope phase (CEP) of the ultrashort pulse. Constructive and destructive interferences in the HHG spectrum resulting from coherent superpositions of electronic states in the H{sup +}H{sub 2}{sup +} system are interpreted in terms of multiple electron trajectories extracted from a time profile analysis.},
doi = {10.1103/PHYSREVLETT.98.013001},
journal = {Physical Review Letters},
number = 1,
volume = 98,
place = {United States},
year = {Fri Jan 05 00:00:00 EST 2007},
month = {Fri Jan 05 00:00:00 EST 2007}
}

Multichannel molecular highorder harmonic generation (MHOHG) from the asymmetric diatomic molecule HeH{sup 2+} in twocolor laser fields is investigated from numerical simulation of the corresponding timedependent Schroedinger equation (TDSE). It is found that the laserinduced electron transfer (LIET) plays a crucial role in MHOHG, which leads to the multichannel harmonic generation from the ground and longlifetime excited states. LIET is sensitive to the phase differences of the twocolor laser pulses, which can be used to control the enhanced excitation (EE) and enhanced ionization (EI) of the system. Both EE and EI have a strong influence on the overall intensity ofmore »

Ab initio study of highorder harmonic generation of H{sub 2}{sup +} in intense laser fields: Timedependent nonHermitian Floquet approach
We present a timedependent nonHermitian Floquet approach for the precision threedimensional nonperturbative calculations of highorder harmonic generation (HHG) rates of the hydrogen molecular ions subject to intense laser fields. The procedure involves an extension of the complexscaling generalized pseudospectral method for nonuniform spatial discretization of the Hamiltonian and nonHermitian time propagation of the timeevolution operator. The approach is designed for effective and highprecision nonperturbative treatment of highorder multiphoton processes in very intense and/or lowfrequency laser fields, which are generally more difficult to treat using the conventional timeindependent nonHermitian Floquet matrix techniques. The method is applied to the multiphoton ionization (MPI)more » 
Drivinglaser wavelength dependence of highorder harmonic generation in H{sub 2}{sup +} molecules
The electronnuclear dynamics of onedimensional H{sub 2}{sup +} molecular high harmonic generation is investigated by numerical integration of the nonBornOppenheimer timedependent Schroedinger equation. It is found that the nuclear motion and electron ionization are more significant for the longer wavelength and the stronger intensity of the driving laser pulse. When the groundstate H{sub 2}{sup +} molecule is driven by a short laser pulse (ten optical cycles in the calculations), a strong signature of nuclear motion is seen in the wavelength scaling (8002000 nm) of harmonic yield, following a {lambda}{sup (78)} scaling law at a constant laser intensity. It is attributedmore » 
Circularly polarized molecular highorder harmonic generation in H{sub 2}{sup +} with intense laser pulses and static fields
Molecular highorder harmonic generation (MHOHG) by a combined intense circularly polarized laser pulse and static electric field has been studied from the appropriate timedependent Schroedinger equation (TDSE) for the H{sub 2}{sup +} molecular ion. It is found that for a particular static field strength derived from a classical model, efficient MHOHG spectra are obtained with maximum energy I{sub p} + 9.05U{sub p}, where I{sub p} is the ionization potential and U{sub p}=E{sub 0}{sup 2}/4m{sub e{omega}0}{sup 2} is the ponderomotive energy at amplitude E{sub 0} and frequency {omega}{sub 0} of the circularly polarized laser pulse. The static field controls recollision ofmore » 
Highorderharmonic generation using gasphase H{sub 2}O molecules
We investigate highorderharmonic generation of isotropically distributed gasphase H{sub 2}O molecules exposed to an intense laser field. The induced dipole of each individual molecule by the laser field is first calculated using the recently developed quantitative rescattering theory. In a thin medium, harmonic spectra generated coherently from all the molecules are then calculated by solving Maxwell's equation of propagation. By using accurate transition dipoles of H{sub 2}O, we show that the harmonics in the lower plateau region are quite different from models that employ the simpler strongfield approximation. We also examine the magnitude and phase of the harmonics and theirmore »