Photodissociation of SO$_2$ as a way to cold atoms and molecules

We discuss the possibility to use the photodissociation of cold SO$_2$ molecules to produce internally and translationally cold photofragments SO and O. It is expected from our measurements of the molecular Stark effect~[1] that the dissociation pathways and excess energies of the fragments are tunable by electric fields~[2]. Cold SO$_2$ molecules are produced by Stark deceleration. We have realized a Stark decelerator that is able to slow down packages SO$_2$ in weak-field seeking levels to a few 10~m/s center of mass velocity. A Stark decelerator with 326~stages is required for this purpose, since the ratio of Stark shift to initial kinetic energy is small for SO$_2$. The photofragments SO and O have triplet ground states, while the ground state of SO$_2$ is diamagnetic. In combination with the photodissociation at the threshold we want to employ this constellation to accumulate fragments in a magnetic trap by dissociating SO$_2$ as it is stopped by electric fields in the center of the trap. \newline [1] J. Phys. B \textbf{39}, S1085 (2006). \newline [2] Phys. Rev.~A \textbf{74}, 040701(R) (2006).