By using the numerical solution of time-dependent shrodinger equation,the paper studies a few factors,such as absolute phase and chirp rate that affect the transfer probability in the process that ultrashort laser pulses interact with three-level Λ-type atoms.It is found that absolute phase and chirp rate are important factors that affect the transfer probability.By modulating absolute phase and chirp rate,we can achieve the maximal transfer probability can be achieved.This result supports the control of transfer probability experimentally.
Single-photon ionization of a hydrogen atom irradiated by two time-delayed isolated attosecond pulses is theoretically investigated by numerically solving the fully three-dimensional time-dependent Schr\"odinger equation. It is demonstrated that the analysis of the angular-resolved electron energy spectrum, showing a complex interference pattern, allows one to completely retrieve the difference between the energy-dependent phases of the electron wave packets generated by the two delayed attosecond pulses. Moreover, it is shown that in the case of a pair of excitation pulses with the same chirp rate, the proposed interferometric technique can be used to measure the difference between the carrier envelope phase values of two attosecond pulses.
Enhancement of the production of cold molecules via photoassociation is considered for the
Cs2 system. The employment of chirped picosecond pulses is proposed and studied theoretically. The analysis is based on the ability to achieve impulsive excitation which is given by the ultracold initial conditions where the nuclei are effectively stationary during the interaction with a field. The appropriate theoretical framework is the coordinate-dependent two-level system. Matching the pulse parameters to the potentials and initial conditions results in full Rabi cycling between the electronic potentials. By chirping the laser pulse, adiabatic transfer leading to the population inversion from the ground to the excited state is possible in a broad and tunable range of internuclear distance. Numerical simulations based on solving the time-dependent Schr\"odinger equation (TDSE) were performed. The simulation of the photoassociation of
Cs2 from the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ to the excited ${0}_{g}^{\ensuremath{-}}$ state under ultracold conditions verifies the qualitative picture. The ability to control the population transfer is employed to optimize molecular formation. Transfer of population to the excited ${0}_{g}^{\ensuremath{-}}$ surface leaves a void in the nuclear density of the ground ${}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ surface. This void is either filled by thermal motion or by quantum ``pressure'' and it is the rate-determining step in the photoassociation. The spontaneous-emission process leading to cold-molecules is simulated by including an optical potential in the TDSE. Consequently, the rate of cold molecule formation in a pulsed mode is found to be larger than that obtained in a continuous-wave mode.