After or Afterwards?

Solution 1:

Sometimes they are interchangeable, but not always. In your example, after is correct but afterwards is not.

Short technical answer – both are adverbs, but after can also be used as a preposition. After as a preposition is used to point the sentence to another place or time. As a preposition, after can come at the beginning of a sentence, at the end of a sentence, or between two clauses (like in your example). An adverb is used to qualify a verb or word group, often on the basis of time or space. It will usually come before a verb or word group, or at the beginning or end of a sentence. In your example afterwards is not clearly attached to the verb in either clause.

http://www.differencebetween.net/language/difference-between-after-and-afterward/