Population transfer of HF molecules in the ground electronic state through multiphoton transition

The multiphoton transition is investigated theoretically by using wave packet method for the ground electronic state of HF molecule. A laser field composed of two overlapping infrared pulses is used in our model, and the ratio of their frequencies is 1:2. States |4,0> and |4,2> are chosen as target states. Calculated results show that the population can be transferred to different target states as the corresponding resonant frequency is chosen. The probability of the population transfer can be controlled by the initial phase difference of the two pulses. When the initial phase difference is of an odd number of π/2, the probability of population transfer reaches the maximal value. When the initial phase difference is of an even number of π/2, the probability of population transfer reaches the minimum value. In comparison with the state |4,2>, the initial phase difference has a stronger in fluence on the population of the state |4,0>.