COULOMB EXPLOSION DYNAMICS OF N-2 IN INTENSE LASER FIELD BY MASS-RESOLVED MOMENTUM IMAGING

The Coulomb explosion reactions of N-2, N-2((p+q)+) --> Np+ + Nq+ caus ed by the irradiation of intense laser light (0.73-6.9 PW/cm(2)) were investigated by high-resolution time-of-flight (TOF) mass spectroscopy and by the mass-resolved two-dimensional momentum imaging (MRMI) meth od. Six explosion pathways(p, q) = (1, 1), (1,2), (1,3), (2, 2), (2, 3 ) and (3, 3) in addition to (0, 1), (0,2) dissociation pathways were i dentified, whose assignments were securely performed both from the mom entum matching between the fragment pair and their correlation with th e laser-field intensity dependence. The MRMI method, which visualizes the radial and angular momentum distributions of mass-selected fragmen t ions on a two-dimensional momentum plane, was used to correlate ion fragments produced after the Coulomb explosion. By examining theoretic ally synthesized MRMI maps, it was found that the momentum distributio ns of the fragment ions in a wide momentum range can be extracted by t he MRMI technique. The relative yields of the explosion pathways at si x different laser-field intensities were evaluated from the three-dime nsional integration of the MRMI maps, and the intensity dependence of the formation of singly and multiply charged parent N-2((p+q) +) ions prior to the fragmentation was derived. (C) 1998 Elsevier Science B.V. All rights reserved.