This is from the Healing library.
Q: Why do I want to have sex with FWS? Submitted by Dlee
A: Upon being confronted with the undeniable reality that their most trusted spouse has betrayed them with another, some BS's experience an overwhelming sexual desire for their wayward spouse. Many couples claim to have had the best, most intense and loving sex of their relationship during the period following the discovery of an affair, (generally a few weeks to several months), often trying new things and experimenting in ways they had never considered before. This phenomenon is termed "Hysterical Bonding.
There is very little information on this phenomenon, but it appears to be a primal, instinctual way for the partners to reconnect and reclaim each other. While it may feel counter-intuitive to the BS; as if they are "rewarding" the WS for the affair, hysterical bonding can be a stepping stone to reconciliation. The intimacy encourages communication and a closeness that may otherwise take some time to re-build.
The occurrence or absence of hysterical bonding does not appear to be an indicator of successful reconciliation. Many other factors, such as the WS's remorse and openness are far more reliable indicators. Hysterical bonding is, however, normal, and nothing for the BS to be alarmed about or ashamed about experiencing. In fact, it has been said it is the one positive in an otherwise long and miserable experience, so enjoy it while it lasts!