forced oscillations

have a look at this graph[opens new window]. Anyone know what type of fit to apply to a curve like this? It is some sort of y=A . exp(....) function but just hitting exponential fit in xmgrace doesnt do anything useful. might have to do with the fact we havent got any data points on the other side of the peek. tell me if you know anything about this type of curves and if there is a easy to apply fit.
if you are wondering where the data comes from come and visit the 1st year lab at schuster laboratory, manchester and have fred loebinger demonstrate it. Dont make any rude remarks about the experiment while he is near you and beware he might try and make you an offer for a physics course at our new uni