  Promising pathways for photoassociative formation of ultracold heteronuclear
alkali metal dimers in their lowest rovibronic levels (denoted X(0,0)) are
examined using high quality ab initio calculations of potential energy curves
currently available. A promising pathway for KRb, involving the resonant
coupling of the $2 ^1\Pi$ and $1 ^1\Pi $ states just below the lowest excited
asymptote (K($4s$)+Rb($5p_{1/2}$)), is found to occur also for RbCs and less
promisingly for KCs as well. The resonant coupling of the $3 ^1 \Sigma ^+ $ and
$1 ^1\Pi $ states, also just below the lowest excited asymptote, is found to be
promising for LiNa, LiK, LiRb, and less promising for LiCs and KCs. Direct
photoassociation to the $1 ^1\Pi $ state near dissociation appears promising in
the final dimers, NaK, NaRb, and NaCs, although detuning more than 100
cm$^{-1}$ below the lowest excited asymptote may be required.
