Counterintuitive alignment of H2+ in intense femtosecond laser fields

The multiphoton ionization of H-2 has been studied using laser pulses of 266 nm wavelength, 250 fs duration, and 5 x 10(13) W/cm(2) peak intensity. Dissociation of H-+(2) via one-photon absorption proceeds through two channels with markedly different proton angular distributions. The lower-energy channel (2.6 eV kinetic energy release) is produced in the bond softening mechanism, which generates parallel alignment. The higher-energy channel (3.5 eV) originates from population trapping in a light-induced bound state, where bond hardening generates orthogonal, counterintuitive alignment.