Enhanced harmonic generation in extended molecular systems by two-color excitation

Numerical simulations of high-order harmonic generation in the molecular ions H-2(+) and H-3(2+) show that two-color intense (I similar or equal to 10(14) W/cm(2)) short(<1-psec) laser pulse excitation produces harmonics at large internuclear distances with larger efficiencies (intensities) at 6 U-p, 8 U-p, and 10U(p) energies than in single-atom single-frequency excitation. The two-color excitation scheme creates efficient high harmonics by first ionizing electrons with a high-frequency laser pulse and accelerating them with lower frequency towards neighboring atoms. Such two-color schemes should be useful for enhancing high-order harmonic generation in clusters.