[en] The efficient formation of ultracold Cs₂ molecules in a low vibrational state of the ground electronic state from ultracold cesium atoms via a two-color pump–dump photoassociation is theoretically investigated. An excited state wave packet is formed by a negative chirped pump pulse, and then is de-excited to the target vibrational state of the ground electronic state by a long dump pulse. The population transfer process from the excited electronic state to the target vibrational state is closely related to the movement of the excited state wave packet. We find that there exists a dump window during the movement of the excited state wave packet. The population in the excited electronic state can be efficiently de-excited to the target vibrational state of the ground electronic state by the dump pulse turned on in this dump window, and the efficiency of de-excitation reaches 67.11%. The population of the target vibrational state can be further transferred to the lowest vibrational state of the ground electronic state, and the transfer efficiency can reach 99.96%. Graphical abstract:

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