M. Schmidt et al., Fragment-emission patterns from the Coulomb explosion of diatomic molecules in intense laser fields, PHYS REV A, 60(6), 1999, pp. 4706-4714
We have systematically studied emission patterns of fragments arising from
the Coulomb explosion of N-2, Cl-2, and I-2 molecules when exposed to inten
se, linearly polarized laser fields. The experiments are performed at 395,
610, and 790 nm, using two different pulse durations (130 fs and 2 ps) and
choosing two different peak intensities (10(15) and 2 x 10(16) W cm(-2)). W
e show that the anisotropy of the emission patterns increases with the numb
er of absorbed photons necessary to produce the parent molecular ion. The s
et of experimental results suggest that the alignment process occurs in the
leading edge of the laser pulse at moderate intensities (<10(14) W cm(-2))
where the multiphoton regime prevails. We explain these observations in te
rms of the rotational pumping model, as demonstrated by statistical simulat
ions of multiphoton absorption and emission. The present study confirms tha
t, in most cases, the confined emission of fragments along the laser electr
ic field is due to the alignment of the transient molecular ions. [S1050-29
47(99)02710-9].