Efficient photoassociation with a slowly-turned-on and rapidly-turned-off laser field

We present a theoretical scheme used for investigating the formation of ultracold molecules via photoassociation with a slowly-turned-on and rapidly-turned-off (STRT) laser pulse, with Cs{sub 2} as an example. As compared with an unshaped laser pulse, this kind of shaped laser pulse has a prominent advantage by which we can prevent the associated molecules from returning to the initial scattering state. Numerical calculations show that an efficient photoassociation can be realized with the STRT laser pulse, which is available in the current experiment as an optical tool.