Dynamic and geometric alignment of CS₂ in intense laser fields of picosecond and femtosecond duration

CS$_2$ is identified as a molecule for which distinction can be made between dynamic and geometric alignment induced by intense laser fields. Measured anisotropic angular distributions of fragment ions arise from (i) dynamic alignment of the S-C-S axes along the laser polarization vector for 35-ps laser pulses and (ii) geometric alignment due to an angle-dependent ionization rate in the case of 100-fs pulses. Results of classical calculations of the alignment dynamics support our observations. By comparing mass spectra obtained with linearly- and circularly-polarized light it is not possible to distinguish between dynamic and geometric alignment. 33.80.Rv, 33.90.+h, 42.50.Vk