Expresses an action that occurs immediately after another action; 'as soon as', 'no sooner than', 'the moment'.
Long explanation:
The ~か~ないかのうちに grammar point is used to express that an action occurs immediately after another action. In English, it can be translated as 'as soon as', 'no sooner than', or 'the moment'. This grammar point is used with verbs only, and the verb appears twice in the construction, with か and ないか respectively.