Phase Dependence of Molecular High Order Harmonic Generation at Long-Range

The physics of high-order harmonic generation in single-electron molecular ions at long-range(large molecular internuclear distances ) is compared for the two proton system H2+ [1] vs the three proton system H(+)-H2(+) via exact numerical solutions of the 3-D time-dependent Schroedinger equation in intense laser fields (I~ 10**14 W/cm2).These numerical solutions show that photon energies can be produced exceeding the atomic cut-off law Ip + 3.17 Up, where Ip is the ionization potential and Up the ponderomotive energy [2]. It is shown that electron recollision with the parent ion and collision with neighboring ions can be controlled by the absolute phase(carrier envelope phase)of a few cycle ultrashort laser pulse.Furthermore the new cut-off law is a sensitive function of internuclear distance thus allowing in principle for imaging of electron states in molecules separated by large internuclear distances R~ 30-50 a.u. [1] A D Bandrauk,H Yu, J Phys B 31,4243(1998) [2] A D Bandrauk,H Yu, E Constant,Phys Rev A 56,2537(1997)