What is "serener"

Usage examples of "serener".

And I assure you, and you will yourself experience it if you test my statements by personal observation, that one never awakens more refreshed, never does there follow a happier, serener and freer morning than after such a successful struggle with the demons.

There was a shattering explosion, a ripping away and a violent change it acceleration, after which the little capsule floated serener into an elliptical orbit, 116.