Coulombic and pre-Coulombic geometry evolution of carbonyl sulfide in an intense femtosecond laser pulse, determined by momentum imaging

The Coulomb explosion of OCS in laser pulses of 55 fs and peak intensity of 2×10¹⁵ Wcm^-2 has been investigated using an ion-momentum imaging technique to determine the shape of the exploding molecule. The results, which are interpreted using a generalized, classical, enhanced ionization model show a range of geometries consistent with earlier measurements on CO₂, exhibiting an enhancement of the bond angle, but no appreciable straightening. Consideration of the pre-Coulombic motion improves the agreement of our results with the enhanced ionization model, whilst revealing the presence of increased molecular bending.