Hyperfine structure of the A¹Π state of AlCl and its relevance to laser cooling and trapping

The majority of molecules proposed for laser cooling and trapping experiments have $Σ$-type ground states. Specifically, ²Σ states have cycling transitions analogous to D1-lines in alkali-metal atoms while ¹Σ states offer both strong and weak cycling transitions analogous to those in alkaline-earth atoms. Despite this proposed variety, to date, only molecules with ²Σ-type ground states have successfully been confined and cooled in magneto-optical traps. While none of the proposed ¹Σ-type molecules have been successfully laser cooled and trapped, they are expected to have various advantages in terms of exhibiting a lower chemical reactivity and an internal structure that benefits the cooling schemes. Here, we present the prospects and strategies for optical cycling in AlCl -- a ¹Σ molecule -- and report on the characterization of the A¹Π state hyperfine structure. Based on these results, we carry out detailed simulations on the expected capture velocity of a magneto-optical trap for AlCl. Finally, using { ab initio} calculations, we identify the photodissociation via a 3¹Π state and photoionization process via the 3¹Σ⁺ state as possible loss mechanisms for a magneto-optical trap of AlCl.