Nonadiabatic effects in long-pulse mixed-field orientation of a linear polar molecule

We present a theoretical study of the impact of an electrostatic field combined with nonresonant linearly polarized laser pulses on the rotational dynamics of linear molecules. Within the rigid rotor approximation, we solve the time-dependent Schr\"odinger equation for several field configurations. Using the carbonyl sulfide molecule as the prototype, the field-dressed dynamics is analyzed in detail for experimentally accessible static-field strengths and laser pulses. Results for directional cosines are presented and compared to the predictions of the adiabatic theory. We demonstrate that for the prototypical field configuration used in current mixed-field orientation experiments, the molecular field dynamics is, in general, nonadiabatic, and a time-dependent description of these systems is mandatory. We investigate several field regimes identifying the sources of nonadiabatic effects and provide the field parameters under which the adiabatic dynamics would be achieved.