no sooner than; as soon as; immediately after
at the thought of; when I think about
座ったかと思うとすぐ立ち上がった。
No sooner had she sat down than she was up again.
電話が鳴ったかと思うともう切れていた。
The phone barely rang before it had already gone dead.
出かけたかと思うと忘れ物を取りに戻ってきた。
He'd hardly left when he came back for something he'd forgotten.