Spatial alignment and orientation of molecules in intense laser fields of femtosecond duration

Abstract

The rotation equation for angle θ between molecular axis and laser polarization direction that described spatial alignment and orientation of molecules in intense femtosecond laser fields has been deduced. A Gaussian laser pulse and the increasing of internuclear distance during the process of molecular muti-electron dissociative ionization and Coulomb explosion are considered. The orientating process of molecules N₂, H₂, CO, Br₂, I₂, CO₂, and CS₂ is investigated by solving numerically the deduced rotation equation for angle. Calculating results show that the linear polarizability and the damping force play an important role in the angular rotation of molecules in conditions of 800nm laser wavelength and 10¹⁵W/cm² laser intensity. Calculating results also indicate that the majority of dynamic alignment for the light molecule N₂, H₂, CO and CO₂ takes place before the molecule ionizes and begins to dissociate. However for the heavy molecule Br₂, I₂ and CS₂, most dynamic alignment occurs during the process of molecular dissociation. The extent of molecular alignment are extensively calculated and discussed.