Molecular high order harmonic generation by laser induced electron transfer with intense ultrashort pulses

Abstract

We present a study of the nonlinear molecular high harmonic order generation (MHOHG) process in the linear one-electron triatomic ion [ H + – H 2 + ] under a two cycle intense pulse ( I > 10 14 W cm −2) and λ = 800 nm. We have solved numerically the 3-D time dependent Schrödinger equation (TDSE) describing the motion of the electron in the presence of such short pulses. We investigate MHOHG for the internuclear distance R = α, πα/2 between the H + and H 2 + , and for different internuclear distance r of H 2 + , where α = E 0 ω 2 is the ponderomotive radius. We show that, by varying the carrier-envelope phase (CEP) of the laser pulse, one can control the direction of the electron transfer which we call Laser Induced Electron Transfer (LIET). We have focused on the case the transfer occurs from H + to H 2 + ( 1 s σ g ) / ( 1 s σ u ) . We showed that the collision of the electron with H 2 + generates harmonics exceeding the atomic recollision law I p + 3.17 U p. MHOHG spectra we obtained show a series of peaks with maxima and minima. The minima are shown to be independent of the symmetry of the orbital, whereas there are dependent on the pondermotive electron energy U p = E 0 2 4 ω 2 , and the electron collision time with the H 2 + .