Greta, Thank you that is how I was proceeding.

Hmm, I am still a time series novice. So this definitely makes my data stationary, though I don't know what to do with it now? I was comparing a serie before and after an intervention. So I was looking at the coefficient for the initial slope then how much it increased after intervention followed by any change in slope trend. The differencing appears to have removed my jump up since I differenced each of the two groups independently. Any suggestions, I know this is a different questions then initially posted?