Formation of Negative Ions upon Irradiation of Molecules by Intense Laser Fields

Time-of-flight experiments reveal a hitherto unsuspected channel leading to negative-ion formation when molecules interact with intense laser fields. Dissociative attachment by low-energy electrons produced in such interactions, and accelerated by the ponderomotive potential, produces anions whose yield depends on laser intensity. The dissociative attachment pattern is dramatically different from that obtained by low-energy electron impact. Angular distribution measurements show that the laser field spatially aligns triatomic precursors ( CS^-₂, CO^-₂) along the direction of the polarization vector.