  The $\imath$-divided powers (depending on a parity) form the
$\imath$canonical basis for the split rank 1 $\imath$quantum group and they are
a basic ingredient for $\imath$quantum groups of higher rank. We obtain closed
formulae for the structure constants for multiplication of the $\imath$-divided
powers. Closed formulae for the comultiplication of the $\imath$-divided powers
are also obtained. These structure constants are integral and positive.
