Experimental study of ultracold cesium atom photoassociation spectrum using an amplitude modulation technique

A high resolution photoassociation spectrum of ultracold cesium atoms is reported in this paper. A photoassociation laser with its frequency red detuned below 6S1/2+6P3/2 dissociation limit acts on the cold cesium atoms in magnetic optical trap and the excited ultracold molecules generated in the photoassociation process are observed. In order to obtain a high signal-to-noise ratio, the trapping laser is amplitude modulated using acousto-optic modulator and the fluorescence signal is demodulated by lock-in technique. The results are discussed using the density matrix equations.