Time evolution of pendular states created by the interaction of molecular polarizability with a pulsed nonresonant laser field

Previous investigations have shown that the instantaneous eigenstates of a molecule interacting via its polarizability with a strong electric field of a nonresonant laser pulse are pendular hybrids of field-free rotational st ates, aligned along the field direction. However, nonadiabatic effects duri ng the time evolution of the initial field-free rotational state could caus e the molecule to end up in a state described by a linear combination of pe ndular states (a rotational wavepacket) whose alignment properties are nota priori known. We report a computational study of the time evolution of the se states. We solve the reduced time-dependent Schrodinger equation for an effective Hamiltonian acting within the vibronic ground state. Our numerica l results show that the time evolution and the achievement of adiabatic beh avior depend critically on the detailed characteristics of the laser pulse and the rotational constant of the molecule. (C) 1999 American Institute of Physics. [S0021-9606(99)00407-9].