MOLECULAR POPULATION TRANSFER, ALIGNMENT, AND ORIENTATION USING CHIRPED PULSE ABSORPTION

We describe a technique for totally transferring the population of a molecular vibronic level to another optically accessible level by chirped pulse absorption. The method can be applied even for nonvanishing angular momentum states where the Rabi frequencies for the transitions depend on the magnetic quantum number M of the states. The population of a large J initial state can be totally transferred to a J'= J + 1 state by R branch transitions with linearly or circularly polarized light pulses with negative or positive frequency chirp if the bandwidth of the chirped pulse is sufficiently small. For an initial state with small J, having P(Q) and R transitions that are closely spaced in energy and within the chirped pulse bandwidth, the situation is complicated by the presence of transitions involving additional nearby J states which can participate in transitions induced by the chirped pulse. For positive frequency chirp, population can be totally transferred to the excited electronic state, whereas for the negative frequency chirp case the population distribution depends on the details of the energy levels and laser pulse. The technique can be employed to align and orient states in which not all the M states of the initial level are transferred to the same branch, but each M state is totally transferred from the initial state. Criteria for this type of population transfer and alignment and orientation are described and the conditions under which adiabatic passage is maintained are discussed.