Spatial alignment of gas-phase polyatomic molecules by an intense laser field

Angular distributions have been measured of Cl+ fragment ions resulting from dissociative ionization of polyatomic molecules CCl4, CHCl3 and CH2Cl2 induced by linearly polarized laser pulses of intensity 1013 W cm-2. Pronounced anisotropy is exhibited in all cases, with Cl+ detected mainly along the direction of the laser's polarization axis, indicative of field-induced spatial alignment of the precursor molecules. The directional properties of the average linear polarizability of the precursors appear to play a key role in determining the extent to which such alignment occurs