Measurement of electric dipole moment of AlCl and progress toward laser cooling it

Compared with atoms, the permanent electric dipole moments and long-range interactions of ultracold dipolar molecules enable convenient manipulation, making them excellent candidates for applications in precision measurements, controlled ultracold chemistry, and quantum simulations. Aluminum monochloride (AlCl) is particularly promising for cold molecule experiments due to its high scattering rate and highly diagonal Franck-Condon factors (~99.88%). However, its electric dipole moment has never been measured accurately. Here, we report measurements of the electric dipole moment of AlCl using its R-transitions in a cryogenic buffer-gas beam source. These results not only refine the ab initio models of AlCl, which required incorporating spin-orbit exchange interactions, but also aid astrophysical models of stellar and planetary evolution that have relied on a substitute value for the dipole moment of AlCl until now. Furthermore, we discuss the implications of these results for optical cycling and the slowing of a cryogenic buffer-gas beam of AlCl.