Velocity Map Imaging and Theoretical Study of the Coulomb Explosion of CH3I under Intense Femtosecond IR Pulses

Abstract

The Coulomb explosion of CH3Iinanintense(10 100 TW cm 2),ultrashort (50 fs) and nonresonant (804 nm) laserfield has been studied ex-perimentally and justified theoretically. Ion imageshave been recorded using thevelocity map imaging (VMI) technique for different singly and multiply charged ionfragments, CH3p+(p=1)andIq+(qe3), arising from different Coulomb explosionchannels. The fragment kinetic energy distributions obtained from the measuredimages for these ion fragments show significantly lower energies than those expectedconsidering only Coulomb repulsion forces. The experimental results have beenrationalized in terms of one-dimensional wave packet calculations on ab initiopotential energy curves of the different multiply charged species. The calculationsreveal the existence of a potential energy barrier due to a bound minimum in thepotential energy curve of the CH3I2+species and a strong stabilization with respect tothe pure Coulombic repulsion for the higher charged CH3In+(n=3,4)species.