FORMATION OF NEGATIVE-IONS UPON IRRADIATION OF MOLECULES BY INTENSE LASER FIELDS

Time-of-flight experiments reveal a hitherto unsuspected channel leadi ng to negative-ion formation when molecules interact with intense lase r fields. Dissociative attachment by low-energy electrons produced in such interactions, and accelerated by the ponderomotive potential, pro duces 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 t he laser field spatially aligns triatomic precursors (CS2-, CO2-) alon g the direction of the polarization vector.