Optical pulse-shaping for internal cooling of molecules

We propose a scheme to use pulse-shaped femtosecond lasers to optically cool the internal degrees of freedom of molecular ions. Since this approach relies on cooling rotational and vibrational quanta by exciting an electronic transition, it is most straightforward for molecular ions with diagonal Frank-Condon-Factors. Compared with schemes that cool rotations by exciting vibrations, this approach achieves internal cooling on the orders-of-magnitude faster electronic decay timescale and is potentially applicable to apolar molecules. For AlH$^{+}$, a candidate species, a rate-equation simulation shows that rovibrational equilibrium should be achievable in 8 $\mu$s. Progress towards the experimental realization of this scheme for rovibrational optical cooling AlH$^{+}$, including the molecular ion production technique, details of the optical pulse shaping, and the state readout scheme will be discussed.