Isospin breaking in the analyzing power of 3H(3He,2H)4He and the inverse reaction.

We have performed a microscopic calculation for the reaction {sup 3}He+{sup 3}H{r arrow}{ital d}+{alpha} with special emphasis on recent measurements by Rai {ital et} {ital al}. of the analyzing power. A detailed comparison is given with the {ital {rvec d}}+{alpha}{r arrow}{sup 3}He+{sup 3}H reaction. The dynamics responsible for deviations from isospin symmetry in the two reactions manifests indeed in different ways. A comparative analysis seems to allow for a better determination of a specific matrix element responsible for the apparent isospin breaking effects in the {sup 3}He+{sup 3}H{r arrow}{ital d}+{alpha} reaction.