Alignment and orientation of absorbed dipole molecules

Half-cycle laser pulse is applied on an absorbed molecule to investigate its alignment and orientation behavior. Crossover from field-free to hindered rotation motion is observed by varying the angel of hindrance of potential well. At small hindered angle, both alignment and orientation show sinusoidal-like behavior because of the suppression of higher excited states. However, mean orientation decreases monotonically as the hindered angle is increased, while mean alignment displays a minimum point at certain hindered angle. The reason is attributed to the symmetry of wave function and can be explained well by analyzing the coefficients of eigenstates.